["A guy asked me on a date one, knowing I was married.  I denied, of course, but was shocked that he didn't care that I was in a monogamous relationship.", "That's the worst. I wonder if he was trying to prove something.", "Or boost his ego? Either way, he didn't succeed."]
Good! I don't know why people think they can get away with things like that.
I was once propositioned to go on a date by a man that knew I was married.  I was not interested in cheating on my husband, and I told him so.