I have no idea if it's the most inflammatory thing he's said. I don't know much about him other than he wrote a video game I've never played. I just saw
http://news.ycombinator.com/item?id=2938141 reference "openness" and was wondering if Minecraft was actually open source, as I didn't think it was. So I googled for license info, and the first thing I found was a quote that wouldn't be out of place in any typical Linux nerd flamewar.
And then I saw the comment about Notch being so respectful and civil and whatnot, and I luled and posted the flame inducing quote.
Not surprisingly, flames ensued.