Is hate speech defined by either federal or state law?

Inspired by discussion in this thread.

Is hate speech defined by law at either (a) the federal level, or (b) the state level by any one of the fifty states?

FWIW, before a more knowledgeable person shows up…

Relevant Wikipedia links:
Special exceptions to Freedom of Speech in the United States, and more specifically, “Fighting words”.

Short version: It seems like the courts have ruled, in the past, that “[words] that by their very utterance inflict injury or tend to incite an immediate breach of the peace” are not constitutionally protected free speech; however, Wikipedia says that the actual words that qualify as “fighting words” get fewer and fewer over time… but provides no cite for this, so I would question its validity.

One of the linked-to references, written by a Canadian professor who teaches American politics, says:

Heh, Wikipedia in action: While I was typing that response, somebody went ahead and updated the Hate speech: United States section. I’ll quote the latest revision:

Hate speech laws are no longer considered constitutional. See R.A.V. v. St. Paul, 505 U.S. 377 (1992).

So you’re unlikely to find a federal or state law regarding hate speech (though some might still be on the books, I suppose).

In that case, a followup question would be: Are there additional penalties if violence-inducing speech (which is illegal, AFAIK) happened to contain hateful material against protected classes?

That is in fact the very question in the case I cited. It holds that you cannot criminalize a subset of criminal speech on the basis of its content.

It gets a bit more complicated when the line between speech and conduct is blurred, and when the speech is proof of motive (e.g. hate crimes).

But the answer in the area of fighting words or incitement (i.e. violence-inducing speech) is pretty clearly that the state cannot add extra punishment because of the content of the speech.