IMHO, calling for the government to violate the Constitution is advocating unlawful activity. There's a fine line; if Piers is calling for an honest and open debate to repeal the 2nd Amendment, that's protected political speech. If he's calling for government to violate the Constitution based on a groundswell of public emotion (which he has been instrumental in shaping), I would have to consider that a direct incitement of unlawful and potentially violent behavior.
He’s a foreign national engaging in subversive activity designed to undermine our constitution and our national security. He really should be deported...at the very least.