Would you say they had no right to do so, provided they were not on private property, were not obstructing traffic, etc.?
I’m not putting you in the position of defending anyone.
The First Amendment only applies to censorship BY THE GOVERNMENT.
You have no ‘Free Speech’ rights when your speech is against another citizen.
“Suppose hypothetically that Lon Horiuchi got killed and the media was hailing him as a hero. The family of Randy Weaver and the Waco Survivors wanted to demonstrate at his funeral against both Horiuchi personally and the practices of the FBI and ATF.”
You are using a hypothetical that does not exist.
IF the protest was against the Government or any of it’s agencies, then yes, the ‘Free Speech’ protection of the First Amendment applies.
If, however, you are protesting a ‘private citizen’ that has no ties with the government and are deliberately ‘slandering’ them with lies, then no, you don’t have First Amendment protections and there are laws and courts that can and will be used to directly address those issues.
The First Amendment does NOT say ‘The citizens shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances.’
It says ‘Congress’. In other words the ‘Government’.
What about at your work? Or on the street? What if I did it on the street, but only spoke to each person once, but did so to everyone in a loud and offensive manner?
What if I stood on the sidewalk on a public street, outside a synagogue and held posters saying Jews should burn? What if I was with several people and we chanted so loud it could be heard over the music of the cantor inside?
Is there no point where the practical application of the first amendment collides with the thoericial ideal?