Sufficiently dangerous speech is not protected (Schenck v. United States, Dennis v. United States). Whether or not this speech was sufficiently dangerous is a matter of debate, but the comment you're replying to is correct.

'Fighting words' as defined by the courts is a very very narrow definition, however, and I've seen a lot of really naive comments referrencing that exemption.

I think it's important to point out that almost every time you think speech is 'fighting words', it's not.

This has been proven in the courts over and over. If some idea or words really anger or disgust you, I can almost guarantee that it's protected speech.

'Kill all the <insert chosen group>' is not.

'Kill those <specific bunch of persons> over there right now' is... probably...maybe.

It's doubtful that the case would even be decided the same way today.

It's true that the definition of 'fighting words' has narrowed considerably over the years, but the Chaplinsky case is foundational to the debate on what counts as free speech and has weighed heavily on subsequent judgments.

It's been nothing but a hypothetical argument from the grab-bag of people looking to silence speech they don't agree with by people who write newspaper op-eds. It's never actually been used to deny anyone freedom of speech.

If I'm wrong, then cite its use.