Thio is ALSO assuming that every match would be played on Pictochat, or that every set will have the stage, or that it would even be a problem in high level play. There are SO MANY assumptions in that argument that it's almost mind-boggling.
First of all, you GROSSLY overestimate how many times that stage would even come up. In terms of matchups, most people aren't 100% aware yet of exactly how that stage favors certain matchups, so many people are going to stay away from it. The stage, admittedly, has a higher chance of crap happening than some other stages... but that means that people are only going to CP to it if they are certain that they can pull the win. For instance, I now know that you are probably crap on Pictochat because you most likely don't play it much (if at all) anymore since it's been banned. Many people are also this way. Wouldn't it make a lot of sense to practice that stage a ton, learn the transformations and how to deal with them (because it's not like they are OHKO win buttons), then meet you (or someone like you) in bracket who can't deal with the stage and take you there, knowing that I'll have an advantage?
The point of a counterpick is to give the loser an advantage. To even the playing field. Otherwise, why do it? I take you to Japes, and the Klap Trap can still hit me. I take you to Corneria, and I can still die from the low ceiling or the lasers. Hell, I take you to FD, and I can still get lip-gimped. You take these things into account when you willingly choose the stage. No one is being forced to play Picto. At all. Have it legal. Either people play it, and its fine (the default), no one plays it because they don't want to (and it doesn't matter whether we ban or not), or you're right and we ban the stage (and problem solved; MLG has already said they are cool with mid-season bans if the case is extreme enough).
There's no problem here. You're making a problem.