I've got a brother very much along those lines. It's totally obnoxious, and he's unlikely to ever change. About all you can do is refrain from ever expressing your opinions about much to him. He sounds like my brother who is constantly scanning the conversation to find a segway towards him telling me that my thinking is all wrong. Eventually, I just gave up trying to have interesting exchanges with him. Whatever he said, I just kind of responded with something like, "Uh huh. Yeah I see what you mean." That got him bored and frustrated. It's like he only feels alive if he's ranting about something.

Just pity him. He's probably extremely insecure at some level. You are not surrendering anything, if you refrain from expressing your opinions to him. You don't have to justify your beliefs to him. He probably engages like this with everyone, and I'll bet he's very lonely. No doubt people find him obnoxious. It's sad really.