I didn't think the neighbor was an over-the-top asshole. All he did was chase a chimp away from his kids with a baseball bat and yell at a guy who just smashed up his nice car. Neither seem out of line, given the circumstances. And hadn't Lithgow's character been on the drug at that point? If the neighbor had seen him during his lucid period, he might not even have known that anything was wrong with him. The guy was kind of a jerk, but not extraordinarily so.
And he did confront the weird dude who was poking around the neighbor's house. That counts for something, right?
And he did confront the weird dude who was poking around the neighbor's house. That counts for something, right?