This is a well written, carefully argued, and astoundingly, even frighteningly given the author's position as an NYU Law Professor, misguided argument for the criminalization of what he defines as "hate speech."
"Hate Speech" is here defined as speech intended to demean the dignity of an individual, "dignity" being the sense that a person is a "citizen in good standing" which itself is a phrase used to indicate whether or not a person can expect the government (or "society"...Waldren is, typically, vague on the subject) to defend the rights of the recipient of the supposed "hate speech."
Racist posters depicting black people as gorillas are the prototypical examples of hate speech used throughout the book, with one or two Islamophobic posters shouting "Muslims go home" thrown in for good measure.
How often do you suppose Professor Waldren has encountered such things around his Greenwich Village digs? I don't know, but I bet the number is somewhat south of one, and herein lies the rub. Such speech is essentially non-existent in 2016 America. The chance that a father, mother, and innocent children strolling down the street will turn the corner only to be confronted with a poster depicting people looking suspiciously like themselves as cockroaches is vanishingly small.
I honestly have no idea what a realistic example of speech that would run afoul of the Jeremy Waldren Hate Speech Police would look like because no modern examples (as opposed to 250 year old examples) are given. Surely he isn't angling to radically rewrite First Amendment jurisprudence simply to squelch speech that almost never happens.
Waldren's explication of the full argument for free speech is missing one of the key tenets. He almost stumbles into it when quoting part of Geoffrey Stone's argument that failing to protect free speech "shows that the government does not trust its citizens to make wise decisions if they are exposed to the expression." Turning Stone around fills in the argument: free speech is necessary because the citizens can't trust the government to make wise decisions when deciding what speech to squelch.
The argument for unfettered free speech is in its essence an argument for the unfettered search for truth. The lurid hypotheticals that Waldren tries to scare us with are surely not the truth. But they are also vanishingly rare. The government is a very blunt instrument. It is not capable of identifying speech that is simultaneously common enough to present a genuine threat to the type of dignity he defends and not, at least, debatable. I find it disturbing that a law professor doesn't quite get this.