It's the strongest Dark-type move, and it's pretty game-changing since every Pokemon holds an item while few don't get great benefits from it.
I think banning an entire move is pretty iffy as well, but you never know. It really is that good.
I stongly disagree with the idea of Banning an entire Move, as...
- All it is is basically a Dark Type Earthquake if the opponent is holding an Item
- The notion of losing an Item doesnt exactly make it broken, as proved by how Trick and Knock Off itself exist in the Metagame (or in KO's case the previous one) without dispute
- Mainly (if not only) Pokemon with STAB really hit hard. And with the most infamous user of the STAB Knock Off, Bisharp, is Banned, only Weavile is another noteworthy user of it (he is the only that comes to mind to me atm).
- Very few Pokemon actually rely on their Item for Viability and/or Usage, as Leftovers isn't what makes Bronzong a good Diggersby Counter, and the Scarf isn't Keldeo's only option, and many (again, Keldeo is a good example) can function just fine without their Item, if not in the proposed Role you use it for.
- Knock Off doesn't even hit very hard on Pokemon without an Item, or an Item that can't be Knocked Off like a Mega Stone. Some have dubbed this "Knock Off dummy" even going as far to use it in context of a Role. Lol switch into your Megamon, or if it's too frail, a Wall that doesn't really need it's Leftovers, like Crobat or Hippowdon because they have Slack Off/Roost.
Now those are the main reasons why I stand on the
no ban side of the fence. It's like Banning Outrage last Gen. because it was powerful, and only had 1 Resistance. The main reason why people would probably want it to go is because of
Bisharp, and the fact that it found whats in been dreaming of in a reliable STAB and Utility wrapped up in one package. But now that it's gone, I can't really see any other Pokemon other then Weavile hitting too hard, and thus
eliminating the fact that it's powerful from the table, and the loss of an Item part of the argument as well as, as I mentioned earlier,
many Pokes in the Tier don't need there Item to be Viable, while those that do such as Porygon2 don't are few (the only one I can think of). Sure it discourages the use of Eviolite, but UU isn't home to to many of those users.
Now there is no doubt at all that Knock Off is a great Move, as it is resisted by few Pokemon, and has a great perk. But so is Scald, with it's few Resistances and chance to Burn and thus increase survivability. Should that be Banned too?
Rather then Banning a Move, lets focus on it's Users. Bisharp was one of them, and it is gone (for that and a number of other reasons). Weavile is another good example that I'll go back to, and it isn't broken enough imo to resort to that. Outside of using it's Power, Knock Off is just another Trick or Low Sweep to me, and even that is only threatening on certain Pokemon.
Doesn't really sound right to me.