People get rights mixed up with things the Constitution forbids government to do. Rights are things everyone should respect, whether or not the Constitution or any rules apply to them.
This idea that only government needs to respect your right to speak freely is kind of weird. Yes, they are the only ones specifically forbidden to censor you, but anyone who censors others is a bad guy. A jerk.
There's nothing special or magic about the Constitution. Documents don't create rights-- rights have existed exactly the same throughout history and prehistory; thousands of years before the Constitution was written. Bad people have always looked for ways to violate those rights. That's what defines a bad guy. The Constitution did nothing but lay out a roadmap telling government what rights it was forbidden to interfere with. (And it has been ignored, so the experiment failed.)
The right way to fight lies and "harmful" speech is with more speech, not censorship. Or, ignore it. If you censor (or demand someone else censor on your behalf), you've already lost the argument.
Someone might be able to tell you not to speak freely while on their personal property-- but in most cases I'll consider them a jerk for doing so. No, this doesn't mean I would use government or legislation to force them to let someone speak, just that in my own mind I will put them in the "censor" category and have no respect for them on this issue.
I respect your right to speak freely, and I respect it hard. No exceptions. I am a free-speech absolutist.
Again, if you don't like what someone says, say something better to counter it. Don't try to forcibly silence them. It's a bad look.
