"tactically useful"?
Temporarily, perhaps. Not in the long run. Imagine that we find that no, that in fact gaydom is something not "biological" (everything's biological but let's stick with this definition), and that with a proper 21st century "treatment" we can get gays to become hetero.
What then of your arguments? They just backfire. It's like the racist argument on how science "says" that the "races" (of course it's not races, it's ethnics) are not different in what comes about intelligence, etc., therefore racism is false. Well, the obvious problem with this argument is that Science is a harsh mistress and it could potentially actually find the opposite to be true (I am not saying it will, I know it even to be really improbable to do so), and so what would that entail, that racism is a scientific justifiable position??
This is the kind of stuff that makes me appalled whenever someone brings up science to prove their moralities. No, thanks I don't need science to tell me that gaydom is a "hardcoded" phenomena for making me respect gays and their rights, just as I don't need Science to disprove racist theories of intelligences and whatever to just disregard the whole Racist stuff altogether from the start.
Don't even give them that ground "well Science says this so", because then these crooks will find ways for science saying "otherwise" and then you are left with a bag of nothing.