For purposes of defining things it's certainly acceptable. To make decisions on how we treat each other as human beings no. And that's my point. There are many deviant behaviours, we all engage in them from time to time. It's doesn't
mean you should be treated any different as a person.
I wouldn't have a problem with your definition of deviance based on numbers if you would simply stick to it.
If homosexuality is deviant only in that it is practiced by a small percentage of the population, then that's fine. Of course, it also means that playing tennis is deviant behavior, but that's okay. Define the word that way, and use it that way, and that's not a problem.
But you are not doing that. You're saying, homosexuality is deviant because it's practiced by a small percentage of the population, but playing tennis is not deviant.
Of course, maybe I'm wrong, and maybe you do think that playing tennis is deviant behavior. But if it
isn't, then clearly there is some criteria
other than just the numbers that makes something deviant or not.
In which case you need to demonstrate more than just numbers to show that homosexuality is deviant.
You have also suggested that it is deviant because many homosexuals engage in anal sex. And anal sex is deviant because the proper place for a penis is not an anus.
Yet other activities which also put the penis in an "improper place" are not considered deviant, so again this clearly is not your criteria for determining deviance.
Finally you say that homosexuality is deviant because it goes against certain cultural norms. Which, as I said before, is fine, if that's how you define deviance I'm happy to accept that by that definition homosexuality is deviant. So is eating with a knife and fork where I live, but that's okay.