Tarmac,
Sometimes, yes.
A real-world example I read about in school:
As desegregation laws began to get passed, a whites-only club owner posted "no animals allowed" on the door, and next to it posted a "scientific" study that proved blacks were not really human.
You guessed it, the govt said he was wrong and that the assertion that blacks were not human was a "lie" that in practice was not protected by the constitution. It never was protected by the constitution as it is not only untrue but inflammatory "incite to riot" sort of nonsense, but it took the creation of laws that specifically addressed that particular lie before it could begin to get stamped out.
Germany has the same problem. The holocaust did in fact occur. Only hate filled racists, bigots, and religious extremists deny this as the evidence and documentation is overwhelming. But spreading lies about the holocaust has real, concrete effects that can ultimately lead to a repeat genocide attempt if not stamped out, so the govt has an obligation to halt the spread of these lies.
IMHO.