Perhaps he thought he was somehow making the community better by his actions (although it's much more plausible to me that he was just ridiculously mind-killed

I don't see a contradiction here. If someone is mind-killed, then from inside it seems like all people with different political opinions are idiots, and the debate would be more rational without them.

Thus in my opinion Eugine completely failed in the lessons about mindkilling and ethical injunctions, and was incompatible with the spirit of Less Wrong.