When I saw the anti-ban side in the OP bring up that it is "within the realm of human ability" to beat MK and they use that as an argument against banning him, I point to all forms of stalling, air camping, planking, etc. The fact of the matter is that they are all entirely beatable and have not been proven otherwise in a tournament setting. Simply put, it's hypocritical.
Yes, and I'm absolutely against banning aircamping because every character should be able to beat it because it's not like the characters doing this (which mainly is actually Wario) are in the air for 8 minutes, unreachable.
Furthermore, infinite Chaingrabs are stalling, too. Stalling is, as defined in the SBR Ruleset:
"The act of deliberately avoiding any and all conflict so that one may make the game unplayable. Running away from an opponent to reach a better position is not stalling, while doing an infinite grab endlessly against a wall is. Any infinite chain grabs must end quickly after 300% has been reached so as to prevent excessive stalling."
I am against banning strategies in general if they aren't investigated, and especially against
banning them if they haven't had any extreme impact on a tournament. This doesn't mean one or two sets now and then, I mean like, really really dominating a tournament by just using this technique.
The IDC, though, is a glitch that can be used for Stalling. Since it's hard to determine if the user of an IDC is stalling or not, the tactic has simply been banned.
I remember people bringing up the comparison with Akuma's Fireball. Akuma's Fireball is in his game and was programmed to work like it is, so it is indeed part of the character.
I'm pretty sure that the developers of Brawl didn't intend to have something like the IDC happen, hence it's a glitch that is able to break the game - thus has to be banned.