How do I tell this guy goodbye?

I've known this guy for a few years. We're both in our twenties. I am a virgin, he is not. He wants to get in my pants. I've tried to be his platonic friend but he can't control himself. I still like him though. Many, many people have told me to stop talking to him, but do I simply ignore him altogether or should I give him a short explanation as to why I shouldn't talk to him anymore?