I once saw a comment from one of the RH fen who has been around since the beginning, and she expressed real surprise at the amount of het fics in the fandom, lol! (The show has so much hoyay that it's shocking there isn't MORE slash, really).

I think every fandom has a lot of slash. LotR is rife with it, actually, although I've read very little (i.e. less than five) fics in that fandom. And actually, none at all in the HP fandom. You can always stay away from what you don't like, esp. in a bigger fandom.