Um...please don't?

I don't understand some people.
If I flat-out tell you that I don't want to hook up with you - because you have a GIRLFRIEND you should probably listen to me!
"You know you love me :)" Yeah, the problem is...I don't. In fact, I don't even like you.
The fact that you're trying to "get with" me while you have a girlfriend is disgusting - but the fact that I tell you I'm not interested and you still try is even worse!

Why do some people have to be like this?