Yeah, I would not consider the server stats the most appropriate way to discredit or not his "unusual" performance... That's irrelevant as he would mostly play MWGG indeed. Even during league practices, he would have a somewhat normal KDR, at times. There was not much competition back when he played, but that's mainly because GES is just a mod with a small community. There is few people that were really committed to this game (and tried to be the "best") because that's just not worth it, there is too much limitations, it's not a game where you can compete well. So if you want to break those limitations, to be better than everyone else is, there isn't one hundred ways to achieve that goal.
Like Roger said, some people are more aware of how far you can perform in this game because they've played GES a lot, and also... I mean, there is other games that are much more competitive and if you've played them, followed the competitive scene a lot, maybe have even been part of it, then you know what's possible and not. Let's face it, the top players of this game who fall under this category, every single of them, have always found BB at least suspicious. There is a difference between being on top and completely crushing the other top players.
I think some of us have proof of him cheating, but not material ones. We've witnessed some odd things (other than a 8:1 KDR) that are sufficient enough to state the obvious. It's not really much about an "overall" feeling, it's more about some details. Now you can never be certain, for sure, and I'm being accused of cheating a lot so that's never something I take lightly. BB is probably a great players either way, he might still have been the best without, but he definitely raised more than suspicions to me the few times I played against him. Some just want to stand out from the crowd, I don't see why GES would be the exception.