Wearing a hat with a racist slogan in support of a white supremacist who inspires the mass murder of immigrants is no different from being an adolescent and not taking off a hat. Both involve hats. I am very smart.
That's a bad example in reference to Pyramidhead's point about speech that actively promotes violence . While those two hat-wearers are not morally equivalent, violence against either would and should be both illegal and treated as morally reprehensible. There is way too much assumption and uncertain inference to go from "he's wearing a hat that people who voted for Trump wear" to "therefore, he's knowingly promoting violence against other people."
The person needs to at least rather directly promote ideas that encourage violence or say things that enable others to target people with violence (such as the doxing Ngo is accussed of), before any violence against them becomes ethically "understandable". And even then, that violence should still be treated as illegal (not all ethically understandable acts should be legal, just as not all unethical acts should be illegal).
As to Pyramidhead's point, I only partly agree. I agree that there is a big moral difference between violence against speech that promotes immoral harm to innocent people and violence against speech that you merely disagree with. And much of conservative ideology (especially white supremacy) promotes harm to innocents, which includes the harm of unequal rights, and the harm caused by having one's poor outcomes caused by the injustice of others be treated as one's inferiority (e.g., that blacks are poor or more prone to crime due to some innate quality). Basically, punching a person who expresses Nazi views is somewhat like the dad of a rape victim who attacks the rapist who just got off on a technicality. In both cases the attack on the fucking asshole is and should be illegal, but I wouldn't personally hold it against them morally or likely interfere (unlike acts that are both crimes and seriously immoral).
But I disagree with the insinuation in "violent speech" that such speech is itself actual violence and therefore, as violence, should not be legally protected. Suggestions that breaking a law might be warranted should not be treated by the law as a though the law was actually broken. That is extremely dangerous and will lead to far greater injustice and harm to innocents than the speech it's trying to eliminate. Unless you have some form of soundwave superpowers, speech is never in itself "violence". It can be a causal factor in promoting violent acts by someone, but an cause of something, especially an insufficient cause like speech itself is, is not the thing itself. Since a person must choose to act on the speech, the prevention of the violence can be accomplished by prohibitions on the physical action. So, only in those rare circumstances where the actor themself has been so coerced (such as with threats) that they essentially did not "choose" to act, is the speech then enough of a direct cause do hold the speaker
legally responsible. That has no bearing on holding them morally responsible, since morality isn't really about actual outcomes but about intended outcomes and if one intends harm by one's speech, no matter the mediating mechanism, then one is morally responsible for that harm.