I voted pro-ban. These are my reasons:
1. MK is the ONLY character to have surgical rules aimed at him just to try to keep him legal. Even with these, he still manages to tower over the rest of the cast AND is still causing controversy to add MORE rules against him (Scrooging & MK cannot CP...CPs...?). LGL sort of contradicts this, but MKs LGL is far less than the rest of the casts.
2. MK's worst MU is himself, and his worst stage is FD, where he still will almost always have the advantage. That is a SERIOUS problem when our game is based off of MUs, stages, and CPing. MK cannot be CPed to put him at a disadvantage. MK's worst case scenario is ICs on FD, and if he bans that, he has no disadvantage, if that's even considered a disadvantage. No other character has this type of CP advantage. The MUs that people claim go even with MK, get torn apart eventually when the MKs learn the MUs (Pikachu, Yoshi, Snake, DDD, Diddy, Falco, etc...)
3. We are trying to cater our stage list to keeping MK legal. This sort of coincides with #1, but is more serious as it affects all characters. Why remove even more stages just because of MK when without MK there is no real problem with them?
4. The last reason is just plain over-centralization. Take a look at doubles, for example. Nearly every team needs at least one MK to keep up. In singles, it's less dominant, but still a pretty big problem, especially when combined with all of the above.
Overall, it's hard to say whether or not MK is "broken" because that depends on your definition of broken. If all of the above falls within your definition of broken, then to you he is considered broken. Either case, I don't see how you can defend him being legal in 2011. In 2009, yea sure, but not now when things are just getting worse.