Limiting freedom of speech is an extermely dangerous road to take.
I agree. And it doesn't work. You can find Nazis in Germany today, and Germany has the most restrictive "no Nazi symbols" law in the world.
The best policy is not to hang them, but rather to give them enough rope to hang themselves.
Consider that George Lincoln Rockwell started in the 1950s. He was in Time, Life, etc. magazines, had numerous TV interviews, was often quoted and interviewed, etc. So they've had almost 60 years of peddling their message and today they are still a small fringe group of nutjobs.
The high point of neo-Nazism in the USA in my opinion was the Order's exploits in the 1980s. The only reason the Order made headlines is that they had the fortune to hold up a Brinks truck and made off with $3 million, which they lavished on other groups. Not surprisingly, these idiots blew the money quickly and everyone associated with the Order is now in prison on lengthy jail terms. The Order was also willing to commit violence to pursue its aims (e.g., the murder of Jewish talk show host Alan Berg) - most neo-Nazis are trailer park losers with dental challenges who sit on their couches, drink beer, and complain.