[devman0]

Compelled speech has lots of examples from warning labels, disclosures, truth in advertising, etc.

What you should be asking is their precedent for compelled false speech, which is a much more interesting and difficult to answer.

[philwelch]

Not just that, but compelled false advertising—false advertising itself already being a federal crime.

[yencabulator]

Many of those seem to be "you cannot do this legally codified activity unless you also fulfill the requirements enumerated therein". Can't sell food in retail setting without labeling it as required in the law that regulates food sales, and so on. That seems separate from compelling a creation of a false statement unrelated to business activity.