I think the technical description of what you are talking about is giving a guy "blue balls." There is absolutely nothing mean about not helping a guy out, because the guy (as can a girl in the same situation) help himself out, as soon as he can get himself to a private area.
At some point, probably around the dawn of mankind, some frustrated caveman discovered that even though he may have been unable to bag the cavegirl of his dreams he could still make himself feel better. And he did . . . Probably again and again and again. Therefore denying a man after a heavy makeout session is really just forcing him to get in touch with his evolutionary ancestors and adapt or perish.
Amen.
luhlz
Good answer. And don't let a guy pressure you into "helping him out" if you don't want to. Make it clear that you don't want to, and if he doesn't like it, find another guy.
What a lovely day for a 2723761! SCK was here