I agree that if you don't want to be involved with him romantically you should not be friends.

Sadly, being friends with someone who pines for you doesn't work out. It is like being strung along. They like you so much, but you don't want them. They are heartbroken. You're just trying to be a good friend. They can't date because maybe you'll change your mind. They can't take the time to heal from the rejection because you're still there. You start feeling rejection because they pull away to heal. See? That's you're whole story.

So, unless you want to try a relationship, I say end it before you both end up being enemies instead.