I disagree, there are some huge practical differences actually. When government gets to decide what political views are not acceptable it results in:
* Potential abuse of this power by (elements of) the government to silence the opposition or hides mistakes;
* Police, army and secret services in time get very close ties with extremists, like it happened in Germany and many other European countries;
* Censorship is done by bureaucracy, and bureaucracy always tends to blindly apply the rules. There are many examples of how this is bad and dysfunctional (e.g. when Uncle Tom's Cabin book was banned for racism);
* These bans are really easy to circumvent, as can be seen all across Europe;
* By forcing extremists to hide their most notorious symbols, you actually make them less horrible and more acceptable to the general public, and it actually helps them to move into a mainstream and spread their ideas. Alt-right is much more dangerous than bat-shit crazy right, because (as we've seen in US recently) it will get traction much easier.
* You can ban nazi symbols, but it will not change a single idea in anyones head, these people will still believe in the same things as they do now.
* equally important: you create a bubble where bad things are boiling in the underground, but general public is not aware of this. Having nazis or KKK freely marching around is a reminder to the rest of people that this threat exists and that things are far from ideal for minorities. If it's the government's job to take care of this then people will leave it to the government, they'll not feel it's up to them to take active part in it.
* and the last, but also important: these people are citizens, with the same rights as anyone else. And with the need to be heard as anyone else. By silencing them you will push some of them into even more crazy extremism and you will give the whole movement the aura of the forbidden fruit, mystery and secrecy and that will make it more attractive to many, especially to teenagers. On the other hand, by letting them march around from time to time you channel that negative energy, they can't complain about being mistreated, and you keep them at bay and their influence marginal.