If you want good writing about nonviolent communication, pick up The Gentle Art of Verbal Self-Defense by Suzette Haden Elgin. It is all about using language with lovingkindness.
I have written about how “Direct Action is for the Privileged,”
Tell that to the slaves who ran away, dropped valuable tools down the outhouse, or revolted and killed their masters. Tell it to Rosa Parks, or Malcolm X. Direct action is for anyone who has fucking had it with people tormenting them, and it can be nonviolent or violent as people prefer. Sure it can get you killed. That doesn't stop everyone. Inaction can get you killed too, and is usually harder on one's dignity and self-respect.
It reduces people to a homogeneous block.
That book might, but nonviolent communication as a concept occurs across many cultures. In some Native American tribes, certain people are not to converse directly, to avoid breaking taboos (e.g. mother-in-law/son-in-law). So they developed a way of "thinking out loud" and communicating obliquely. This minimizes both the risk of sexual entanglements and arguments.
It’s classist. It assumes all people have access to language in the same way and hypervalues people who have more awareness of grammar, word choices and sintaxe construction.
No reason you can't talk sweet in your milk tongue.
I have always been amused that when her (male, upper-class-speaking) colleagues said Ozark English was an inferior dialect, Suzette disproved the claim by writing an academic paper in it.
All speaking people have access to language, which they can use as they please, gently or harshly. Nonspeaking people have other modes of communication which can also be gentle or harsh.
I found myself frustrated because of the hyperattention and hypervigilance of NVC practitioners, which translates to “If you’re not meeting my standards, then you’re failing at NVC,” and the discussions ended up being more about why I chose XYZ word rather than actually addressing the issues.
No, if you're being a dick, then you're failing at nonviolent communication. It's all about reducing friction, saving face, and not making other people feel bad. You can't make an ugly topic less ugly, but you can certainly refrain from making it worse with poorly chosen words. The whole point is to diffuse pressure before a difference becomes an argument becomes a fistfight. The moment you try to use the techniques of nonviolent communication to hurt people, it ceases to be nonviolent. Nobody said doing it was easy.
It doesn’t embrace nonverbal communication.
Definitely read The Gentle Art books, and if you can find it, Try to Feel It My Way, the touch-dominant handbook. Nonviolent communication relies heavily on voice tone and rhythm, also somewhat on body language.
As an example from my own experience, when a tall person takes care not to loom over shorter people, that's nonverbal nonviolent communication: "I am not a threat." This sort of thing is not as widely practiced as it should be, so that may explain why many people don't notice it or do it.
It gives the oppressor the tools to appear more loving, kind, and thus morally superior, while not having to do any work on the actions that precedes language.
Only if you're easily fooled.
Here's a general piece of advice to avoid that issue: whenever the words and the actions disagree, believe the actions. Words lie; actions don't. A person who speaks softly but violates your boundaries is not nonviolent. Indeed, gaslighting is a form of abuse that specializes in making the victim look bad while the abuser seems calm and reasonable. Just because someone isn't yelling doesn't make them nonviolent. Not harming people makes you nonviolent: ahimsa, in Buddhist tradition.
Nonviolent communication is a way of moving gently through the world, treating yourself and others with kindness. It needn't be your only tool -- I can still stab someone in the reality tunnel if necessary -- but it should be your routine way of interacting with people you care about, and it is a good first several lines of defense in dealing with hostile people. It is also a most excellent way of undermining violent regimes, because they can no more understand it than Sauron could imagine that Frodo meant to drop the Ring down Mount Doom, and also because it can be the record that breaks the record player.
Like most pacifist techniques, this doesn't look like much until you develop a lot of skill, and then it is downright overwhelming. You can assist your opponent to the floor, using his own momentum, as effectively with nonviolent communication as with aikido. In most cases, it is not necessary to do violence in order to stop a conflict, merely know how to block and defuse and dissuade. There are many different variations on this theme according to culture, and you may use the one(s) you grew up with or choose anew, as you wish.