What I find hardest to defend is priestly celibacy, especially after the sexual abuse scandals still rocking the Church.
The leadin is normally a statement to the fact that the speaker doesn’t agree with it and that all the problems of sexual misconduct would greatly diminish if this was done away with.
Most times I’ll give a non-response along the lines of, “You’re not going to convert me, I can’t convert you. So I don’t discuss things of this nature, it’s a waste of time for both of us.”
Not ideal but it’s the best I come up with. “Mind your own damned business would be the alternative.”