Also that's not true at all - Ghost Bisharp does not appreciate the Koff when there's STAB behind it, and now you actually resist it's Sucker Punch so its all well.
252+ Atk Gallade Knock Off (97.5 BP) vs. 4 HP / 0 Def Bisharp: 139-164 (51.1 - 60.2%) -- guaranteed 2HKO
No STAB, removing an item.
252+ Atk Gallade Knock Off (97.5 BP) vs. 4 HP / 0 Def Bisharp: 208-246 (76.4 - 90.4%) -- guaranteed 2HKO
STAB, removing an item.
Both on a Bisharp that's added Ghost. If it hasn't added Ghost, time for Close Combat regardless, and if's part Ghost you don't need STAB to remove more than half its health. Without STAB the second Knock Off won't be a KO, but if you're running Electric Gallade with Thunderpunch you just do this-
252+ Atk Gallade Thunder Punch vs. 4 HP / 0 Def Bisharp: 160-190 (58.8 - 69.8%) -- guaranteed 2HKO
-to finish it off. Or you could just smack it twice with Thunder Punch, even if it's not Ghost. (What, you really think
Ground Bisharp is going to happen? Grass? Electr-actually does Bisharp get Electric moves 'cause that could actually happen)
The STAB only really helps if you're planning on running a Physical Psychic move for STAB (Such that Ghost Bisharp is untouchable for your other STABs), and I stopped doing that almost immediately in ORAS OU because
Psychic is a crappy offensive type. It also is a set that Ghost Mega Tyranitar will completely laugh off, Dragon Dance, and then murder your entire team if you don't have Mega Scizor or something (Mega Gallade meaning you don't have Mega Scizor), it's completely walled by Mega Sableye, it's not actually any better against Ghost Bisharp than Electric Thunderpunch Mega Gallade, etc.
I'd
much rather run Close Combat/Leaf Blade/Knock Off/Will O Wisp with added Grass typing (To counter Mega Tyranitar, in part: Will O Wisp it and then Leaf Blade it) or Thunderpunch over Leaf Blade and Electric typing, or even Fire Punch and Fire typing to laugh in the face of Will O Wisp, which is one of Mega Gallade's worst enemies. (Fire Punch would be a OHKO on Ghost Bisharp, by the way, barring Focus Sash, which STAB Knock Off does nothing to help push through)
There's other examples as well of mons that don't mind a non-STAB Koff but might worry about a STAB Koff.
Name them, because your examples thus far are flatly wrong.
What you said about Psychic- and Ghost-types is just not true, especially in a meta where anything can become a Ghost or a Psychic.
The part where Psychic is almost invalidated by Ghost, or something else? I'm not actually sure what you're trying to say with this sentence.
I mean look at something like Steel / Psychic Cresselia - you're not going to tell me Cress is frail, are you?
252+ Atk Gallade Knock Off (97.5 BP) vs. 252 HP / 152+ Def Cresselia: 288-338 (64.8 - 76.1%) -- guaranteed 2HKO after Leftovers recovery
252+ Atk Gallade Knock Off vs. 252 HP / 152+ Def Cresselia: 192-228 (43.2 - 51.3%) -- 5.9% chance to 2HKO
STAB removing an item followed by not removing an item. Pretty neat.
252+ Atk Gallade Knock Off (97.5 BP) vs. 252 HP / 152+ Def Cresselia: 192-226 (43.2 - 50.9%) -- guaranteed 3HKO after Leftovers recovery
252+ Atk Gallade Knock Off vs. 252 HP / 152+ Def Cresselia: 128-152 (28.8 - 34.2%) -- 2.5% chance to 3HKO
Not STAB, removing an item followed by not removing an item. Not 2HKO, fair enough, and with Swords dance the STAB one
will be a OHKO while the non-STAB one has a small chance of being a OHKO.
On the other hand...
0 SpA Cresselia Moonblast vs. 0 HP / 4 SpD Gallade: 192-228 (69.3 - 82.3%) -- guaranteed 2HKO
This is zero investment, no buffs on Dark/Fighting. With investment...
252 SpA Cresselia Moonblast vs. 0 HP / 4 SpD Gallade: 256-304 (92.4 - 109.7%) -- 50% chance to OHKO
So even without a Special Attack boosting nature or one Calm Mind, it has a 50% chance of OHKO-ing you while you're messing it up with a Knock Off. The double Fairy weakness doesn't matter? Really?
Then there's any number of bulky Normal-types that might want to try on their Ghost pants - something like, say, Ghost / Normal Chansey?
Eviolite Chansey is stupid if it's staying in/switching in for your Knock Off, STAB or no. But hey let's calc it anyway.
252+ Atk Gallade Knock Off (97.5 BP) vs. 4 HP / 252+ Def Eviolite Chansey: 552-650 (85.9 - 101.2%) -- 12.5% chance to OHKO
STAB on Ghost/Normal.
252+ Atk Gallade Knock Off (97.5 BP) vs. 4 HP / 252+ Def Eviolite Chansey: 368-434 (57.3 - 67.6%) -- guaranteed 2HKO
No STAB on Ghost Normal.
Small chance of being a OHKO on STAB, true enough -but they're
both 2HKOs (Knock Off does the same damage against an Eviolite target as it does against something with no item) if you don't get that 12.5% chance of a high roll, and they're
both OHKOs if Chansey is stupid enough to come in while you have a Sword Dance up.
As for Fairy- and Poison-types, well, Fairies can generally only take either Close Combat or Zen Headbutt, but not both (obviously they can take about 1 or 2 before dying, but it will be doing a significant chunk if you hit them on the switch).
Steel-type Togekiss laughs in the face of your ignorance, and is a thing, and is vulnerable to Thunderpunch while walling your entire set.
252+ Atk Gallade Knock Off (97.5 BP) vs. 248 HP / 0 Def Togekiss: 108-128 (28.9 - 34.3%) -- 99.7% chance to 4HKO after Leftovers recovery
Simulated Knock Off. Crap damage.
252+ Atk Gallade Zen Headbutt vs. 248 HP / 0 Def Togekiss: 60-71 (16 - 19%) -- possible 8HKO after Leftovers recovery
Simulated Zen Headbutt on Steel variant. Even more crap.
252+ Atk Gallade Close Combat vs. 248 HP / 0 Def Togekiss: 135-159 (36.1 - 42.6%) -- 94.8% chance to 3HKO after Leftovers recovery
Such crap damage it can literally switch in on it and murder you. Targeted against a pure Fairy to simulate Steel lowering resistance by one tier.
Meanwhile...
8 SpA Togekiss Dazzling Gleam vs. 0 HP / 4 SpD Gallade: 360-424 (129.9 - 153%) -- guaranteed OHKO
Nil investment, effortlessly destroys you, no matter what.
Meanwhile Electric Gallade...
252+ Atk Gallade Thunder Punch vs. 248 HP / 0 Def Togekiss: 338-398 (90.6 - 106.7%) -- 43.8% chance to OHKO
... does
this to Steel-typed Togekiss.
Why is Zen Headbutt supposed to help against Fairies again? Togekiss is one of the most common Fairies in the meta -after Azumarill, I think- and utterly destroys your set and demolishes your statements. Heck, Electric Mega Gallade takes halved damage from
both of Togekiss' STABs compared to Dark Mega Gallade.
Speaking of Azumarill...
252+ Atk Gallade Knock Off (97.5 BP) vs. 92 HP / 0 Def Azumarill: 125-147 (34.3 - 40.3%) -- guaranteed 3HKO
STAB
252+ Atk Gallade Zen Headbutt vs. 92 HP / 0 Def Azumarill: 69-81 (18.9 - 22.2%) -- possible 5HKO
STAB against a Steel variant -and note this isn't that bulky of an Azumarill (surprised that OU Belly Drum isn't bulkier) and also note that even with resistance it would
still be crap.
252+ Atk Gallade Close Combat vs. 92 HP / 0 Def Azumarill: 310-366 (85.1 - 100.5%) -- 6.3% chance to OHKO
Tiny chance of a OHKO against a Steel typed Azumarill. Again, with low bulk on the Azumarill, so more realistically it'll be tougher. If you have a Swords Dance up, great! Oh by the way let's imagine for a moment it's Fire typed instead -which Azumarill
runs in Hidden type- because at that point the above numbers are what you get
after a Swords Dance with your Close Combat while your Zen Headbutt that's supposed to "counter Fairies" does...
+2 252+ Atk Gallade Zen Headbutt vs. 92 HP / 0 Def Azumarill: 275-324 (75.5 - 89%) -- guaranteed 2HKO
...
this. ie not good enough, and
again this Azumarill has low bulk.
And nothing enjoys switching into Koff for the sole reason of item removal - losing your lefites makes you so much easier to wear down.
Don't need STAB for that.
Any type that wants to resist / be immune to Psychic with Fairy is susceptible to neutral Close Combat, which is awesome.
See: Steel or Dark Togekiss, Dark Gardevoir (Resists your entire set), Dark Mr. Mime by the same token, Flying Klefki or Mega Mawile. (Flying Mega Mawile was a thing before OU banned Mega Mawile, and was quite good)
No.
Also Ghost being everywhere makes Knock Off useful, and Dark-types useful for neutralizing your Ghost weakness, something that would destroy you otherwise. It also lets you resist Dark, which is good because Dark is such a good offensive typing.
Ghost mostly occurs on a few specific Pokemon that it is enormously useful on, and of course natural Ghosts, who are rarely vulnerable and in any event are generally so fragile you don't need STAB to murder them. Calcing Gengar... well, it can revenge switch if you don't have STAB and can't if you do, so that's
something, but if the idea is you're going to Swords Dance while they switch out whatever is scared of you or whatever, then STAB, again, stops being necessary at all.
Also I don't see your point about SD - you should never set-up until you have a general idea as to what type your counter is, which you can do by just attacking them on the switch.
You use offensive set-up moves either when the enemy can't KO you in a meaningful time frame or when you expect them to switch in something that the set-up move will give you an edge over, at which point it becomes
crucial that you don't know the typing of an enemy in Hidden Type automatically -if you assume that Clefable is Steel and Close Combat it with your Swords Dance up and
oops it was Fire type, you're dead. If you Zen Headbutt it assuming it's not Steel type and it is, you're dead. Etc. You are
not going to attack them on the way in, figure out their type that way, and then Swords Dance -because they'd KO you while you're doing it.
Psychic isn't great offensively, but it works well enough to fend off Fairy-types.
Given that no Fairy/Poison or Fairy/Fighting type exists and Hidden Type Fairies don't have overwhelming reasons to add either, no it doesn't. You are underestimating the bulk of Fairies
enormously.