I actually don't think it's funny.

I mean, I know it's unlikely, but what if he saw all the stuff that's been posted?
He's like an ex-scientist, I'm sure he could figure out how to find a blog if he really wanted to.
Again, I'm sure he'll never see any of your uncalled for remarks, but still-this is cyber bullying. And this kind of stuff is what leads children, and I'm sure also, adults, into bouts of depression and other social disorders. From these they can deal with life long trauma that can also lead them to do really bad things in order to seek revenge, make themselves feel better, and so on. Even though you're joking, some people may not see it that way. Please think twice before you say something about someone, even if it is behind their back.