There is a pretty big difference between ignoring one commenter who doesn't like you and ignoring the complaints of a large proportion of the community. This wasn't just one or two people kvetching. It was a large number of people, including many (like me) not directly targeted by the behavior. I don't think you have any obligation to respond to gwern, but if a significant segment of the community objected strongly to your allegedly trollish behavior, and some valuable contributors said they no longer felt comfortable participating on LW because of that behavior, I would consider it "pathological disregard" for you to continue what you were doing as if none of this was happening, without addressing it in any way.

Keep in mind that Eugine continued (surreptitiously) with his block-downvoting not just after a number of users expressed their dissatisfaction, but also after the administration of this site made it clear they disapproved of the behavior. First Eliezer said that he was trying to track down the block downvoter (he failed for some reason), then Kaj put up this post. And Eugine kept down-voting. I don't see how this doesn't read as disregard for the community.

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, since virtually all of the block-downvoting appears to be motivated by political disagreement), but he was still doing it in the face of the community's express wishes, and to the evident detriment of community relations. Thinking that his behavior would make the community better/more successful is so disconnected from the reality of what was actually happening that it qualifies as pathological disregard for the community, I think. Disregard for what people think and how they feel, and disregard for the observable consequences of his behavior.