I was a student at the 2018 racket school mentioned in the link.

All of the instructors, including Felleisen and Butterick, were nothing but helpful and friendly inside and outside of the classroom.

Even taking that link completely at face value that Felleisen is a Torvalds-type asshole in certain personal interactions... his work including How To Design Programs had such a positive impact on my life and the lives of others that I wouldn't discourage people from taking advantage of it.

This is a very personal conflict between prominent community members. The larger racket community is very friendly, including the core team.

Felleisen is an insufferable prick but also easy to avoid. More a symptom of an illness in academia than Racket specifically, I'd say. In the community there are some 'weird nerds' with strong opinions that are likely to be more annoying since their presence is more strongly felt, but that's just how it is in many social settings where money doesn't chain things down.