Bull shit— You cannot tell anybody what to say!!
Laws do it all the time.
Drug ads must disclose drug side effects. Celebrities acting as TV pitch men have to say that they are being paid to promote the products. Most states have laws compelling doctors to tell women information about their baby before they can perform an abortion. Political ads have to say whether they are endorsed by the candidate. TV used to have a "fairness doctrine" which was repealed by Congress, but its constitutionality was upheld by the Supreme Court.
I could give you 100 examples.