I don't know that I would go so far as to say it's exactly homophobic in some way, but it's on the same spectrum.

And I am a little offended that you put same-sex pairings context as incest. I am not insinuating that you were lumping the two together, but there is a big difference. Chiefly: Incest is wrong and pretty gross, and being homosexual is perfectly natural and normal.