In the grand scheme of things, whats the difference between being gay & incest?

I know the actual difference, but they both can be looked at as odd sexual preferences depending on whom u question the oddity. I'm figuring you have to be born with both instances of these preferences, so, that's a pretty even playing field.. Is it that the gay community is just large enough to command acceptance? If there where a group large enough to fight for incest would that be accepted by culture eventually? Is it all just a game of numbers? I'm not advocating gay or incest, just interested in hearing how our culture valuates it's tolerability... Just a question...