Do you feel guilty if someone undesirable won't give up on befriending you or hitting on you? How do you deal?

UUGH! That drives me batty. I can't stand a person who thinks just because they find you attractive, that automatically you will be hooking up with them. I actually said to a guy once that it was wrong for someone to think that, and he still didn't get it. I had to come right out and tell him to stop hitting on me. I think it probably helped him in the long run, because he won't do that in the future to other girls and waste his time.