Provided something isn't offensive, it's fine.
How about this one - heterosexuality is obviously the normal genetic set-up for humans. Anything other than that is a biological abnormality.
That sounds, on the fact of it, homophobic. But it's obviously not - the "default" setting for humans to procreate is heterosexuality.
The problem is that people will equate that to "morally wrong" rather than "genetical suboptimal". Strangely, I can't actually think of a way to put it in a "science" way that makes it homosexuality sound OK, because if you're looking at it in a coldly scientific light, it's the "wrong" sexuality.
Instead of the question being "Is is nature or nurture?", the bigger question is "Why does anybody give the slightest toss either way?" - if someone is gay, then they're gay. For me, it's no more a factor than someone having dark hair, or long fingers, or they can roll their tongue etc.
Religious nonsense has a lot to answer for in terms of promoting intolerance based on stupid things IMO.