Uh, Its because he's a dumb 10 year old going through puberty - he gets off on letting people know about it.
Wow, you really despise him, don't you?
But it's truth.
He's only posting pics of women because he thinks it makes him 'cool', trying to prove he's mature. I personally think guys who think of women as tools, are indeed immature and should stop living in the 1800s. However, this issue cannot be solved, just like every other never-ending existing issue, such as pollution, poverty, senseless violence, drugs, power-hunger, waste of nonrenewable resources, and racism.