When Harry Met Sally.

Harry: You realize of course that we could never be friends.
Sally: Why not?
Harry: What I'm saying is - and this is not a come-on in any way, shape or form - is that men and women can't be friends because the sex part always gets in the way.
Sally: That's not true. I have a number of men friends and there is no sex involved.
Harry: No you don't.
Sally: Yes I do.
Harry: No you don't.
Sally: Yes I do.
Harry: You only think you do.
Sally: You say I'm having sex with these men without my knowledge?
Harry: No, what I'm saying is they all WANT to have sex with you.
Sally: They do not.
Harry: Do too.
Sally: They do not.
Harry: Do too.
Sally: How do you know?
Harry: Because no man can be friends with a woman that he finds attractive. He always wants to have sex with her.
Sally: So, you're saying that a man can be friends with a woman he finds unattractive?
Harry: No. You pretty much want to nail 'em too.
Sally: What if THEY don't want to have sex with YOU?
Harry: Doesn't matter because the sex thing is already out there so the friendship is ultimately doomed and that is the end of the story.
Sally: Well, I guess we're not going to be friends then.
Harry: I guess not.
Sally: That's too bad. You were the only person I knew in New York.