GP may be disingenuously trying to square the circle by turning this story around on left-wingers, but you are wrong: one does not have to be ignorant to see that left-wingers restrict speech all the time. I am very left-wing and I am disgusted by the fact that left wingers try and succeed at restricting speech in the U.S. and abroad. To me, it flies in the face of what progressivism should be about.
What you are missing is that both left and right wing restrict speech in America, Saudi Arabia, Holland, etc. It is a phenomenon that occurs, regardless of ideology, when people get to a point where they see themselves as the sole judges of what is good and righteous, whether they are Mullahs or elected officials in a socialist country. Maybe given enough power, you could get frustrated enough to restrict GP's right to blame things on left wingers, or I could restrict your right to make gross generalizations about right wingers.
In the US, the left wing often tries to suppress speech through social means like shaming people and protesting un-P.C. speech. They try to tell people which words they can and cannot say. Worse, as mentioned above, many progressive European countries without our history of codified "free speech" have actual laws against denying the Holocaust.
Incidentally, if I were an adolescent growing up in Germany, the fact that it is illegal to deny the Holocaust - which is on its face a crazy opinion to have - would make me think that paradoxically there might be some truth to Holocaust denial. After all, why are they trying to stop discussion about it?
In America, we let idiots like Fred Phelps and company spew all the hatred they want, without fear of official reprisal. It makes it easier to keep tabs on them and to know what we are dealing with. In countries like Germany, forbidding people to speak openly about their history has arguably aided the resurgence of neo-naziism.
Moreover, restricting hate speech makes it harder to keep track of these hate groups and to know what their true goals are. The smarter/saner ones don't dare deny the Holocaust in public. Many of the most powerful neo Nazis are polite businessmen in suits and ties, hiding in plain sight like an antisemetic Gustavo Fring.