1. Running into someone you otherwise respect, who’s saying things like an idiot or a crazy person.
2. Defending the person you respect by attacking this idiot/crazy who’s using their name.
If it makes people feel better who run into this peril, it also used to happen back in the days of paper fanzines and letters to the editor. It has been suggested that this is one of the reasons people wanted conventions and clubs so badly, so that they could know what their favored sf people were really like. A personal meeting can often explain a lot.
And actually, it’s sort of a karmic revenge of the rational side of someone’s personality upon the irrational side, like Old George Lucas finding himself attacked for not being as cool as Young George Lucas (or the version let through by his editing friends and wife). Some people can be very savvy and freedom-loving in the incidental bits of a piece of art, and then say the exact opposite with the bits of the story they think are Important Speeches. For example, Mercedes Lackey is the sort of writer who has her characters go to great pains to save baby birds and pregnant mother animals, while then sending them off to kill unborn baby humans with palpable authorial approval. And this goes on practically in the same chapter, because it’s never too much trouble to save animals but it’s obviously always too messy to help females and young of your own species.
Self-publishing can reveal some of this, too. I’ve seen a fair few authors reveal the uncut versions of their old stories and novels. Sometimes the uncut version is clearly better, makes more sense, and becomes the ur-version in my mind. But there have been times when I’ve been startled at how stupid or counterproductive or physically impossible the new version is, and clearly some people need an editor’s help. For example, Steven Goldin’s uncut version of Jade Darcy and the Affair of Honor. The mass-published version is a comfort read for many. The self-pub version starts with a flashback nightmare of Jade being raped which is not only calculated to make the browser put the book back on the bookstore shelf unread (and possibly to “trigger” reactions in people who’ve been raped), but has some details about hair which seem impossible for human female physiology. Gentle Reader is torn between disgust and laughter.