unquestionably provide instructions for a leftist resistance willing to use violence
Exactly its resistance. Violent resistance to fascism is morally correct. Dude basically admitted that resisting fascism is against his ideals.
Also it definitely should have been aired. There are lots of songs out there describing much worse things that get aired without issue. Art is not legal advice and lyrics dont have to only contain things that are legal. And they werent planning to air it without comment, but with loads of context and discussion.