Unfortunately, I wish it were that easy. But in reality, criminalizing certain speech does not suppress it or prevent people from holding those opinions.

Björn Höcke, the leader of Germany’s far right AfD party, was convicted of using Nazi slogans, and Germany has very clear laws preventing Nazi speech.

And yet, AfD is now the country’s 2nd most powerful party.

Sadly, criminalizing bad speech does not change the minds of those who hold those opinions, nor prevent their spread.

"In this one specific case, convicting this one specific person didn't destroy the whole movement."

Well, no; because they haven't gotten together the political will to outlaw AfD itself as a Nazi party.

This doesn't show that banning the speech doesn't work; if anything, it shows that being overly tolerant of Nazis...lets the Nazis stay around.