My guy friend was being a d*ck to a girl, she now likes me..?

So I'm 20 and this girl is 19, my friend is 23.

Anyway, my friend wanted to "get" with this new girl at work which I thought, alright fair enough.

A few weeks passed and she absolutely hates him.. I approached her and asked what's going on.

She said that he doesn't want to be friend unless they sleep together. Now, to be honest I thought that was a slack move. I told her to forget about him, I invited her out to lunch and we walked for a bit around the pond, fed the ducks and stuff.

I wanted to get to know her, the more and more we talked, the more we began to trust each other.

Anyway, she likes me. I like her, my friend how ever thinks I am a dick for "stealing his bird" and telling her all the bad stuff he has been saying about her.

I like my friend, he's a good guy, but when it comes to girls, he's horrible. I want him to move on, and hopefully learn from this situation, that not all girls are looking for one night stands.

How do I get him to calm down and accept that he screwed up, I'm not the problem, but the way he treated her was?