No, it is a limit on free speech but it is one of several that various governments (and cultures as a whole) throughout the world have upheld fairly consistently. Free speech is more or less an unachievable platonic ideal that we aspire to. Success varies, as do the compromises made along the way.
Speaking more generally, don't let your ideals bias your judgment. Just because you support policy X and also view ideal Y as good that doesn't mean that X isn't detrimental to Y. It's important to be objective about these things.
> Free speech is more or less an unachievable platonic ideal that we aspire to
I’m almost certain it’s shorthand for “freedom of expression”, which most reasonable people throughout history have not grouped threats of violence into.
In fact, they’ve done violence in return, historically, in response to credible threats, and some jurisdictions uphold that legal right.
I'd counter that freedom of expression is either equivalent to or a superset of freedom of speech. The specifics are purely an argument of semantics and thus most likely uninteresting and not worthwhile.
Most reasonable people throughout history have not attempted to defend any sort of blanket right to make threats of violence in any and all circumstances, I obviously agree with you there. My point was that this is clearly a restriction on the freedom to express oneself. I don't know how to articulate my reasoning here any further because the meaning is about as literal as you can get. A threat of violence is most certainly an expression made by an individual after all.
It isn't always desirable or even possible to achieve a platonic ideal that we otherwise generally recognize as being good to strive for. However pretending that we aren't making carveouts leads to muddy thinking and paves the way for abuses.
Speaking more generally, don't let your ideals bias your judgment. Just because you support policy X and also view ideal Y as good that doesn't mean that X isn't detrimental to Y. It's important to be objective about these things.