Book burning: agree, and I feel like I've read somewhere, I don't remember where or if it was reliable, that Fritz later regretted his impulsive action

Found it: Catt, memoirs, v.1, p. 29. I don't see it in the account of this episode in the diary, although it may be elsewhere, or Catt may be writing down something he remembered in the memoirs, or Catt may be making things up, either because he believed Fritz was sorry or thought that he should be.

Only slightly less of a betrayal than book-burning: book falsification. Curse you, Catt!