Trust me. No one is ignoring the heterosexual wedding market.
Here's the question: odds are pretty good one of my grad school colleagues will have a homosexual wedding at some point. If he were to invite me to the wedding, what should I do? Ignore him? A card saying "I wish you the best" is probably not a bad choice.
UH, can’t you just send a generic card? Does it have to be homosexuality based?