Intense and prolonged anger has a way of interferring with higher cognitive functions. He's not mentally ill, he's just very, very pissed, and he knows that he doesn't know what he's talking about.
You've probably had some education dealing with conflict management, so you would be aware that there are basic goals most people strive to achieve in conflict situations.
In these forums, the most common goals are either Win-Win or Win-Lose, and sometimes Compromise. Ryan knows that he's overmatched in any conceptual engagement, so Win-Win is not an option, and Win-Lose is just too distasteful because he would always end up losing. And Compromise is too complicated, so that's out also. So it ends up that Lose-Lose is his best bet. He doesn't mind losing--as long as you also lose. To him, that is a way to finally see himself as being on equal ground.
You have the dynamic correct, however you may not have access to all the data. He has been crazy from day one. He has Delusional Disorder, Paranoid type. Yes, he has anger issues on top of that.