That's not what the tone argument is, though. It's pointing out behavior exactly like Jim Butcher's here--refusing to accept as valid any of the legitimate issues this person raised because s/he was angry and used a four-letter word.

I won't argue the fact that people sometimes hide behind the tone argument as an excuse to be assholes--the social justice movement, like any other movement, is comprised of people, and people tend to be assholes--but I don't see how that's the case here. Butcher is using the tone argument in a classic way--"You weren't nice enough when you called me out on my racism, therefore nothing you said counts, you are a bad, mean person, and I am a victim of the PC brigade."