That's quite an assertion, but I notice you back it up with nothing at all.

What you describe as the libertarian version is the non-cartoon version of "First Amendment absolutism": you can say what you want, but you're not immune from demonstrable consequences of what you say. There's nothing in that position that requires or suggests that people should be coercively prevented from speech that is unpopular, incomplete, or incorrect. In that light, the objections you present mostly fail to address my point.

The only exception is your extension of the FDA and FTC rules regarding food and drug advertising to non-advertising speech, which would present a lot of practical problems, creating a vast opening for frivolous and harassing lawsuits against public figures and discouraging the expression of much valid and worthwhile opinion. I'd oppose it, and I can't imagine that it would find support outside the sort of election-year rhetoric that evaporates on contact with reality.