Another ignorant antiban point is 4MSS.
4 move set syndrome means that a pokemon needs more than 4 moves to be effective. Take for example Lucario or XY metagross. They needed a 5th move to be effective in the meta. for example, Lucario wants SD, espeed, close combat, iron tail and ice punch. Landorus I is by no means whatsoever a victim of 4MSS. It does not need 5 moves to be effective in any regard. All of it's sets are incredibly efficient and dangerous to all playstyles. This is a pokemon who can freely change up it's moveslot to nail counters without losing any sort of effectiveness. If anything this just shows how disturbingly versatile and dangerous it is.
I will go ignoring the fact that you are already trying to discredit anti-ban side caricaturing their agruments, I could do the same by just shitposting "LOL pro-ban side are so weak they just wanna ban a mon they can't kill while it's easy as fuck" but I won't
Poeple are talking about 4 MSS because Landorus-I actually needs to make a choice to kill his checks/counters :
Latias-Mega : Landorus-I has no way to win 1v1.
Cresselia : same as above.
Mandibuzz : same as above.
Lati@s : Landorus-I needs U-Turn / Knock Off.
Zapdos : Landorus-I needs Rock Slide.
sDef Talonflame : same as above.
sDef Charizard-Y : same as above.
sDef Gyarados : same as above.
AV Tornadus-T : same as above.
Gengar : Landorus-I needs Psychic / Knock Off.
If you take into account Landorus-I always run Earth Power / Focus Blast / Sludge Wave, you see there is a 4MSS.
I know team support required to beat them is pretty small (scarftar beat a lot of them for example), but these mons also have team support, so "SR weakness" is not a good point imo.
And anyway, if you ban a mon because it is able to beat his checks/counters, then you have to ban every dragoons and even more.
Moreover, Landorus-I is "slow", 101 BS speed isnt huge, it's outspeed'd by a plethora or threats in the metagame (Manectric, Lopunny, Thundurus, Keldeo,...), and it's not mentioning all the priority users (Azumarill, Scizor, Weavile,...) if you are concerned by RP.
All in all, to me Landorus-I just seems to be a pretty good mon for Offensive team, like Greninja was, without the speed tiers that made made Greninja broken.