1. The problem with saying a sterile person has an excuse is that you are inferring that they are somehow flawed or IOW, need some excuse and that is just so wrong on so many levels. What of those who choose not to have children and there are many who don't. Are they, too, excused? You use the word excuse and its like some child that has an excuse for not having done their homework. It means in some way the person did something that they need this excuse for and it may be that they were born sterile. In that case, would not have God made them sterile and if so, why would they even need this excuse?
2. Being gay has, or rather is, being traced to be genetic. If that is the case, and you believe God made you, would that not mean that God made them gay? Being gay is not about physical desire Ether. Its an attraction to the same sex. You reduce being gay to nothing more than sex and that is just wrong on so many levels. Do you honestly think that all that gay people do is have sex? Its a ridiculous way of seeing being gay. In your relationship with your wife is all you do have sex? If not, why would you think that of a gay couple?