I do it for a lot of selfish reasons too.
I like arguing (not with dumb people). I learn a lot by arguing with intelligent people.
A few years ago, I was part of a community of super smart people, probably 80% were smarter than me, and I loved the discussions. We constantly tested ideas and checked boundaries. There were no sacred cows.
Seriously, it is exhilarating to start a conversation with someone, and they understand opportunity costs, Lockean Homesteading, etc. You don't even have to explain or repeat that taxes are theft because it's not only understood, it's already incorporated into the ideas which will be discussed.
These posts, while I don't mind doing them (most of the time), it's like putting on your shoes. Over and over again. You keep putting on your shoes. One day, you get lucky, and you can tie the laces.
But you never leave the house, because the discussion never advances that far. Next thing you know, you're back to putting your shoes on.
People are entitled to believe whatever they want. In a lot of cases, people believe things which are implicitly and explicitly dangerous to me. I try to be tolerant of this because I can't do much, if anything, to change it, and because you can't reason with people who rationalize violence.
I don't resent a Lion for wanting to eat me, I don't resent ignorant people for wanting to enslave me.
I have made my peace with that. On the one hand, I don't want to have done nothing, and on the other hand, I know that profound change is probably beyond my conventional lifetime.
Deep down, I am hoping for the singularity.