Personally I always found that the women who I knew that insisted on "couples" showers were the very clingy/insecure ones.
Ouch.
Anyway! My bridal shower will be a "girls only" event (with me and all 4-5 of my female friends
) but only because my OH could not give a shit less about that. He actually wanted to be a part of the baby shower and so he was. If my OH said to me "I'd really like to go to this baby shower" and I said no, then MAYBE I could see how you'd call it discriminatory, but I think overall guys just don't care if they're a part of showers.
I've imposed my way into guys' poker nights in the past because I like poker and I like to drink beer and I didn't want to spend my Friday night alone because I have no penis. But I also accept that sometimes my OH just needs a night out with his guy friends to do guy things, just as I go out for dinners with my girl friends without our OHs. I don't think it's discrimination to not invite your spouse/members of the opposite sex to EVERYTHING you do.