As someone who likes slash, femslash, and het, I don't really see a problem with 'het only' or 'slash only' comms. But to define themselves by what they don't like, i.e. 'non-slashers' versus, say, 'genfics only' or 'het-shippers', seems as if they are going out of their way to be actively anti-slash. I wouldn't want to associate with them, but I wouldn't necessarily judge anyone who did based on that summary.

Plus, they didn't ask you if you wanted to join, and that just seems kind of rude that they couldn't be bothered to ask you if you wanted your fic included in the first place.

But that's just me. It's your fic, and you should do what makes you happy :) Fanfic should not cause stress, lol.