The blatantly false part I'm talking about isn't "Mark Zuckerberg is endorsing Trump" which everyone understands to be the obviously false statement, but the subsequent argument that is still being repeated here that "If Trump tries to lie in a TV ad, most networks will refuse to air it."

A whole bunch of comments here are along the lines of: how come Facebook isn't required to abide by the rules that other media companies have to follow? But this is the exact opposite of how things are - small media companies can adopt whatever standards they want, but the broadcast networks have to air even false political advertising, because these types of regulations are more about protecting fairness and free political speech than about the truth. This is an example of Facebook subjecting themselves to the highest possible standards, instead of making arbitrary editorial decisions that smaller actors can get away with.

It's not the same high standard when they allow targeting of specific people and groups highly vulnerable to bullshit with no one else included who might identify it as such.

How would this be any different from advertising on certain shows or talk radio that peddle huge amounts of BS and are almost exclusively consumed by gullible people?

Again, the point is that the standards followed by broadcast TV are higher than the standards followed by, random media companies that aren't regulated. And what Facebook is doing here aligns closely with how public institutions that are held to the highest standards operate. The general principle regarding the freedom of speech is that the closer you are to being a public institution, the more open you ought to be in terms of the types of speech you accept.

So the criticism here isn't merely wrong, it's exactly backwards.

I can freely choose what shows, radio stations and other media I see, and see the same ads as their audience. In the case of targeted ads, I can't move from demographic to demographic as I please, so some campaigns are inaccessible to me.

To me, that opaqueness separating one filter bubble from the next is an important quality. It may raise the effectiveness of propaganda campaigns significantly.