As a homosexual I am completely unable to emphasize with cultures and nationalities that kill my kind. Many of us think like that, but embedded in the „left and liberal“ groups we often are and the threat of violence from watermelons, we need to hide our real opinion.
Though Hamas as argument is good enough. With the support they enjoy among Palestinians, a distinction between civilian and hamas fighter is generally not possible.
It's justified for gays to support Israel on the grounds that Israel is socially liberal (or that Palestinian society is illiberal, which it is).
It's not so smart for gays to be cavalier about 'left and liberal' groups considering how recent and how tenuous any tolerance of homosexuality is within right-wing and conservative groups.
That might be a horribly obvious and boring thing to write, but it's the sad truth.
