Well, I'm not omnicient, so I don't know what the guy wanted. But it doesn't make any difference. None of this was coincidental. Ray Nagin wasn't taking his daily walk around the city he did his best to destroy when he noticed this guy's signs and thought to himself, "I'll just go in and try to talk him into taking down these "offensive" signs. While it doesn't bear on the free speech considerations, it beggars the imagination to think all this fire power just happened to show up on the guy's doorstep. Which is not to say they don't have a right to show up, it's to say this was an attempted mugging. And it doesn't impress me that heavyweight local pols want to shut somebody up because they don't like the content of his speech. And you keep referring to the mob as his "neighbors." Well, they all presumably live in NO, but that doesn't really make them "neighbors." This was a rent a mob, whistled up to participate in this mugging.
As to your hypothetical, the Supremes have already ruled on WBC's rights. And insofar as surrounding Freddie and his band of merry makers is concerned, the actions to be taken to protect them would vary with the threat, don't you think? If it's a loud standoff, like in the parking lot of a death house on execution night, then no harm no foul. But somebody pulls a gun, hits Freddie in the choppers (which I would pay to see) or credibly threatens violence, then the cops are legally bound to protect him and his free speech rights.
You say the man has the right to his opinions. I agree. But the city councilman shouldn't use her power to shut him up. Really, don't you agree with that? I mean, shouldn't city councilmen be more concerned about picking up the trash, and schools, and street repairs and not the political views of their constituents? And if her argument is some reference to "disruptions" caused by the mob, move the mob along. That's what cops are for (even in NO).