the answer is quite simple.
Yes, gay sex, or any sex for that matter outside of marriage is sinful. Just as telling a lie is sinful.
Now that doesn’t mean it has to be unlawful anymore than telling a lie (under most circumstances) is not unlawful.
But sinful and unlawful are two entirely different things.
It occurs to me that this could be an artful way of answering the question in a very honest and Christian way – just start off by pretending to misunderstand the question:
“Is homosexuality sinful?”
“Do I think the politicians should outlaw it? No, I do not. We don’t need laws against homosexuals. We don’t need to hunt people down and oppress them over this. Who believes that is a good idea? Certainly not me!”
“No, no, no. That isn’t the question! Is homosexuality sinful?”
“Of course. Read the Bible. Anyone who loves someone and wants what is best for their soul should encourage them to repent of their sins. All sins. Lying, stealing, adultery. Homosexuality is certainly one of the things which is sinful.”