Given where those arguments have lead before -- the holocaust -- is allowing people to advocate for those viewpoints truly harmless?
And keep in mind, all the people who profited off that war: IBM who made the punch cards to track those interned, Ford motors who built the rail tracks for concentration camps, Ford himself who had his employees hand out anti-semetic propaganda, Prescot Bush/American Standard Oil who sold oil to both sides .. all these companies funded and benefited greatly from the results of that conflict.
By focusing on the Nazis you ignore the fact that wars needs funding. Few of those who funded and profited from that conflict were ever held accountable.
Modern neo-Nazis are the modern boogieman. They make us afraid, but unless they are funded, their reach is quite limited. They are loud, but easily ignored. Those who give them a voice, news and media outlets, do so to profit from the readership.
I'm not saying I agree with it, but when trying to feel out the contours of an issue like this, it's important to start at the edges.
The issue of when ideology and ideas become actively "harmful" or "dangerous" is an extremely complex one with a ton of grey area. It makes sense to start with the extreme cases where some of that grey area is removed. Those who argue that it makes sense to actively work to silence certain ideas argue it on the basis that those ideas represent a real and present danger to their lives and safety.
This certainly goes for Jewish people, like me, arguing against an ideology that promotes genocide of us based on our heritage -- I'm not even religious nor do I identify that strongly with jewish tradition, but based on the Nazi's accounting I'd have been sent to the concentration camps. People voicing support for those ideas are essentially saying I should be murdered for no good reason.
I hold it's reasonable to feel threatened by that and even to react to that with violence. Though it's not the strategy I adopt or recommend, it's one I feel a reasonable case can be made for.
Move in towards (ever so slightly) greyer cases. Take for instance people of color arguing against ideas that they feel would marginalize them for the color of their skin. What's the history, how much do those ideas represent a clear and present threat to these people's safety? In the case of those arguing in favor of, say, more militarized and aggressive police -- you could make a decent argument that this represents a real and present threat to black people's safety, given the prevalence of police shootings. Similarly, support of more profiling of brown people or requiring papers for immigration status. That represents a certain threat to the safety of perfectly legal brown people in the case that they are profiled and detained because they can't produce their papers.
All I'm saying that this is a huge grey area and that it is important to recognize that some ideas, beliefs, and ideologies are not harmless and do on their own represent varying levels of threat to other people.
Words are not harmless. The pen can be mightier than the sword and it can cut both ways.
Could I maybe inquire why Stalin, Mao, Pol Pot and Che who wiped out a lot more people than Hitler and whose images ( especially Che ) show up quite prominently on T-shirts worn by people on the coasts do not trigger the same kind of hysteria?
We can't just ignore the fact that there is a well reasoned argument there in favor of treating certain ideas and ideology as active violent threats.
It's also a real and present issue to many people in the current climate.
I don't like religion for example and would like organized religion to be illegal in my country. If I went on TV and said this I bet this would be a very unpopular opinion and people would most likely send me tons of death threats. I think this mentality is stupid and if you are upset the correct assement is not being a child about it but actually proving me wrong by arguments and facts.