The best argument would be bringing up that (if I remember correctly) nothing in the new testament actually directly addresses homosexuality or condemns it as such, and that all the stuff in the old testament was thrown out when the old covenant was replaced.
So if the old covenant, and everything in the old testament along with it, was replaced then all that homophobic stuff was thrown out as well and there's no reason to believe that god wants you to act on that scripture that condemns homosexuality, because you know, he threw it all out and told his followers to disregard it.
But I'm not a Christian (and BTW never have been) and it's a long time since I read the Bible, so I probably butchered that.