One of my legal classes was a "US Constitution" and it was about Constitutional Rights (in Canada there is Charter of Rights).
While US law has less restrictions (for example First Amendment has no "reasonable limits" clause and, subsequently, there is no degree of free speech that can be restricted on the speculative grounds of where the "reasonable limit" line is), yet it does not entitle anyone to limitless exercise and abuse of such right.
For example, you can't go to movie theater and scream "Fire!", causing panic and mayhem. Also, Supreme Court ruled on "fighting words", which means you can't go around and call people names and obscene words that would provoke even a reasonable person to a physical response (we studied a case when someone used obscene words related to intimate intercourse and mother of the person it was addressed to, which resulted in a blow to a face of the insulting party. Courts ruled in favor of cursed party and said that "fighting words" are not protected speech).
Also restricted under our law are words causing violence, death and destruction (Cosa Nostra mafia head can't verbally order assassination of the enemy, and then claim in court that he didn't do it , just spoke what the thought. You can't as well stand on a soap box, gather people around you , enrage them and cause them to start a riot, burn cars and cause other destruction and violence. Under the law you could be held personally liable for causing such mayhem).
But who is advocating here for such abuse of rights and who is crossing the line here?
If anything, I make a clear distinction between free political speech and personal attacks, and demand that those who disagree with me express their disagreement on merits of the argument rather than resort to name calling, bullying tactics and vitriolic replies full of venom and ad hominems. aimed at coercing me into silence.