Curiosity Killed the Cat

This morning I decided to log on to Facebook and see what'd been going on in the stalker-feed. Not much, people adding things to their profile, leaving groups, making friends, what have you. Then I notice it. Up in the corner. "You have been poked by Ex-Boyfriend." This caused some head-tilting confusion (apparently I'm all about the hyphens today) since the last communication session with him involved him voicing (well, typing actually) his concern about having relationships with two different girls. My response was sort of a kiss-off, and I didn't hear from him for months. Then this. Not even a note or a brief email to say Hello. Just a poke. It's been bothering me all day. I should warrant more than a poke. Especially considering the mental turmoil that he always manages to stir up whenever I have some form of communication with him. We parted ways on -- not bad terms, but obviously not good ones. There was talk of remaining friends. I'm always skeptical of that, because it rarely works, and never in my experience. I did though, because I still retained the misguided hope that he and I could somehow, someday, have a relationship again.
I haven't been considering that in quite some time now. With Ex-Boyfriend living in another country, I was able to gain some perspective and see what a dysfunctional relationship that was for both of us. Several of the conversations that we had as "friends" enabled me to move on and focus on myself. I am a different person now than I was when he and I were together. I feel more myself than I have in years. Stronger. More confident.
All of these things are a little threatened when he pops back into my life. He talks to me and treats me the same as when we were in a relationship, and that chafes me now. I want to assert myself to him, but I am afraid of his reaction. Will he disdain me even more? Will I be seen as one of the fools he was so quick to identify as useless? Another question is why his opinion matters to me as much as it seems to. If I would rather not communicate with him at all, why do I care what his opinion of me is?
I definitely wish that I could go through the rest of my life without interference from him. But at the same time, I can't seem to let it go when he does something like this. One click of the mouse and he's got me on the defensive. I guess that I could just say that it's the drive to know "Why? Why? Why?", but that doesn't seem satisfactory. It feels like there is some deeper reason than simple curiosity at work here. I apparently welcome the obsessive state that communication with him puts me in. Am I a glutton for punishment? Or am I striving to best him at some undefined and ultimately useless contest of wills?

I just don't have the answers.