Chiroptera already touched on the first thing I was going to mention and that was “Assuming homophobic means ‘hates gay peoples’ as opposed to ‘fears them’” moving on…
I suppose it depends on the tone and who it’s coming from. It could be said in such a way as to mean “I don’t care if people are gay as long as I don’t have to see it” I think that’s fine. You have to remember, as accepting as you may want other people to be, they’re still allowed to not want to see two guys kissing, they’re still allowed to be grossed out by it, for that matter, no one has to like the fact that other people are gay, all they have to do is not act violently/rudely/physically on those thoughts. (I think that’s what I’m trying to say).
OTOH, someone else could say it and very much imply that homosexuality is a horribly sin and people should be locked up for even thinking about it.
Also, that statement only says that (again, it seems to be in the tone) the speaker could never be with another person of their own gender it doesn’t say anything about how they feel towards other people that are gay.
To use another example (that I see on preview). If I say, seeing someone eat mushrooms makes me want to puke and I think people should eat mushrooms out of my sight, it doesn’t mean I hate those people, it simply means I would prefer if they would keep that one activity out of my sight. Granted, people generally keep sex (gay or otherwise) out of sight so it’s not a perfect analogy.*
Something else this reminds me of. I was listening to someone on a talk radio show and he commented on how when discussing gay relationships, everyone always goes right to the sex part of it. For example, you ask someone about their feelings about homosexuality and they make a statement like in the OP right off the bat without even considering all the other things that happen in a relationship (shopping, buying a house, going to a movie, having a fight, vacations etc), it’s always “that’s gross” or “how does it work in bed”, or “I don’t care what they do behind closed doors”.
*I wonder if this is what makes it slightly homophobic now that I think about it. People generally keep sex out of sight so you CAN say something like “I don’t care what they do behind closed doors” without coming off as a homophobic jerk since you’re not asking them to change anything while still getting your point across. OTOH, most of those people probably wouldn’t be okay with straight people having sex out in the open either, so, maybe not.