I think the issue of whether or not homosexuality implies sterility is tied to the argument that homosexuality may or may not be genetic, rather than a conscious choice by the individual. If it's a choice, then it's perpetuated as a meme and fundamentalist Christians are free to argue that it should be outlawed. If it's genetic, then one could argue back that "God made me/him/her that way" and therefore homosexuality in God's eyes must be okay.

Not that I think either party is correct, personally. But that's a discussion for another node.