Check out his antics on LWN sometime. He is biased out the ass (at times outright being a lobbyist) and quite unpleasant to boot. Many of his "tactics" reek of bullying, such as insisting that people who he disagrees with reveal their personal details.

See this discussion for one relatively tame example of why people intensely dislike the guy: http://lwn.net/Articles/437650/

For extra fun, in this discussion he seems to be entertaining himself by attacking PJ's gender.