Why? What interest does an explicitly secular government like that of the United States have in legislating religious morality in order to make homosexuality illegal?
Similarly, what interest does any state have in criminalising voluntary actions between individuals? Particularly ones where no rights are being infringed on, there is informed consent and no individual harm.
Or, are you in favour of a theocracy of some kind - whether formalised, normative or just putative - that enshrines Christian strictures into legal code? And, if so, what other behaviours are you in favour of criminalising (or permitting)?