That's probably because Hilde's shit is worst than all of those mentioned above, or at least considered so by the rest of the community.
You can't blame people for how they feel. The majority of the players that were "booing" aren't even hardcore SC players. Basically, people don't like to see/play/learn broken shit, no matter how much you want to "cover it up", broken shit is broken shit.
I never thought of big events like EVO to be recruitment spots, but rather a showcase to reveal what the game has to offer, and what needs to be fixed. Like Sagat in SF4 for examples, there were enough public complains that capcom officially admitted he is overpowered, and thus likely to be fixed in the future. Since we all know where Namco/soul team stand in terms of balancing the game, we need to do the same.
As far as recruitment goes, pretty graphics, pick up and play, advertisement (/w boobs) is all you need to attract the casual crowd, and guess what, SC has them all. To actually strengthen the community, we need the fighting game crowd, and you only get that by showcasing a balanced and fun gameplay with plenty of depth and diversity. SC4 DOES NOT HAVE THAT RIGHT NOW. As I said, Namco does not care about us, because we mean nothing to them (no profit), so we have to find ways to make them care. IMO, one of the best way to do this is by embarrassing them in front of their core consumers (fighting game fans) in events like EVO, so if they want their game to be considered a "fighting game" at all, they HAVE to put the effort and time to play test the next SC game.
Again, good balanced games attract followers by themselves (look at blazblue), broken shit attract nothing but shit no matter how you sugar coat it. For the good of the soul series, speak up and make them care. I rather have 1000 random people on evo chat saying SC is shit than to have another SC3.