Zuck's response was, "well, I think it's BAD if you LIE. Telling lies is bad." but wouldn't say that Facebook would moderate that kind of content.
I personally don't see a legitimate free speech claim saying that political parties should be allowed to target opponents with plain, simple falsehoods like that (which already happen through the mail system, mind), but I'm open to hear.
I ask because speech is already restricted when it comes to advertising; companies are compelled to put up disclaimers, the FTC will come down on misleading ads, etc.
So, if society's surviving okay with those restrictions, is there a reason that political chicanery shouldn't be held to some standard also?
What is the free speech argument for not drawing a line at that?