Wow, seriously. It's a reductio ad absurdum. Adams tells a story that uses Brice's and the tyrannical left's own version of tolerance to demonstrate that Brice is intolerant. I'll repost the last three sentences to demonstrate that it's reductio. Which, apparently you've never encountered before.
"He might throw another hissy fit, which would lead others to say that gay activists are nothing more than emotionally inferior lunatics. Such speech would promote stereotypes. And that’s the kind of speech that goes against our collective values.
Wherever you stand on this issue, it is clear that we need to exclude non-conformists who do not share our collective values. How else are we going to promote diversity and inclusion?"