Yeah, because mainstream has totally ruin everything!
Being mainstream in and of itself isn't necessarily a bad thing, but it does have some
unfortunate side-effects.
The fact of the matter is that the Internet is chock-full of jerkasses, douchebags, ****wits, morons, trolls, and all other manner of unpleasant people. They're out there, and they will *always* be out there - such is the nature of the beast. While there are a number of ways to deal with such folks (each with varying degrees of success), one of the best is to simply never draw their attention to begin with.
The KS community is, as far as online communities go, relatively small. It definitely has some influence beyond its own circle, as we've seen in the memes and such - but it's still a relatively self-contained entity. The nature of the game itself is partly responsible for this -
Katawa Shoujo is one of those games that you either 'get it' - understand it, *feel* it in a very personal way - or else you don't 'get it' and you end up wandering away, shaking your head in confusion and disbelief. This makes it a rather obscure (and thus unappealing) target for trolls - most of the people who are familiar enough with KS to even realize that a fanbase exists are going to be the sort of people who liked it and don't *want* to hurt peoples' feelings. By its very nature, the 'feels' of KS draw in people who are thoughtful, sensitive, and open with others - which makes for a very civil and enjoyable community.
If KS *were* to ever gain more mainstream acclaim, it would undoubtedly draw more attention from GIFTs eager to bespoil such a fertile paradise now that they would be aware of its existence. Let's all be thankful we're still off the proverbial radar for now, and enjoy the warm fuzzy fandomness while we can.