MTB, he wants to keep some sort of connection or "hook" (as in a thorn in your side) with you. He also enjoys twisting your words and getting you upset. Hey, ANY reaction is better than none at all. I agree w/anvil ... you can't zap him off the planet, but you can get off a site when he's there. He's trying to maintain his image of control over you, even if it's in cyberspace.
Log off when he's there. Sure, he's being a pain by stalking you onto websites you frequent, but he's sick. He's doing what sick people do. Stay on the sites and ignore him, or log off when you see he's on. Perhaps if you do that for awhile, he'll get the message. You called him, and he got just what he wanted in his mind.
I truly understand your outrage at having your boundaries disrespected, but that's what they do in any way they can do it. The way I've protected my boundaries through my email accounts and this site was not to post SR to my "favorites" tab and I use handles and passwords AH would never guess in a million years. I learned long ago not to trust him and what little I can protect privately from him, I do.