A few points / food for thought:
As far as competitive gaming goes, nothing legitimate should be banned until it begins to over centralize the meta-game. Has ANY infinite over centralized the meta-game (yet)? No, and that alone should be enough NOT to warrant a ban.
This is why items are banned. Without consistent, defined spawn rates, they add random chance to matches, which in itself over centralizes any match.
This is why flat stages are banned. The ease of DDD's CG combined with such stages would lead to over centralization (not to mention all the other horrible implications flat stages have to offer).
This is why MK isn't banned- overpowered, undoubtedly, but not to such an extent that he's unbeatable by top players using other cast members, and as such isn't over centralizing the meta-game. However, I admit he does come close due to his ease of playability.
Furthermore, "Anything that can be mastered, will be mastered." True, but the difficulty of any technique must also be considered. This is why we don't see a plethora of IC players in the tournament scene, and also why DDD's infinite is so devastating.
Another thing that must be considered is that these decisions are made from the perspective of top level tournament players. What I'm getting at is while the existence of DDD's infinite might discourage the usage of a few low tier characters, there will still be individuals who will progress the meta-game of these characters, though, slower than that of high tier characters since this will only be readily achieved on a regional basis.
As has been mentioned, banning infinites:
1) Is difficult to achieve (at what threshold do we label something an infinite?)
2) Leads to a slippery slope (why not ban Pika's CG against Fox?)
3) Arguably hurts the progression of the meta-game (nobody searches for solutions to these infinites, possibly leading to fewer discoveries...?)
The main problem that seems to be stemming from these infinites is rofl match-ups, correct? Why aren't we taking a more proactive approach to this problem instead of trying to make such a blatantly polarized decision?
My suggestion would be to take a strong evaluation of clearly biased character match-ups, and then make a revision on how character picks are made in a tournament setting. In the first match of a set, when the blind picks lead to such a rofl match-up, the disadvantaged player should have the opportunity to counter-pick, followed by the opportunity for a counter-pick from the other player. Rinse and repeat until there's no rofl match-up. For obvious reasons, this rule would only be applied to the first match of a set. Just an idea, as this would easily allow for more character diversity in the tournament scene, but still preserves the techniques in question.