I could do that, yes, but I do know him in person, and we have a couple of common friends, both online and offline. If I just cut him off I'm worried he'd start badgering these common friends. Whereas if I just slowly taper him off, he might think I'm just not posting and not bother anyone. And hopefully forget about it.

At least, I hope so. So far, nothing yet, so I count myself successful.