Firstly, that is _not_ what reductio ad Hitlerum means.
More importantly, it's not a fallacy. It's pretty well documented by now that what you get when you have a social network with very little moderation is, almost inevitably, a social network for Nazis:
Just because people like bringing up Nazis a little too often doesn't mean every reference to Nazis is fallacious. Sometimes, it really is about [neo-]Nazis.
The exact fallacy that occurs (almost all the time) when you invoke Hitler is called poisoning the well (https://en.wikipedia.org/wiki/Poisoning_the_well). You are trying to make a position indefensible by associating it with an indefensible thing, without properly justifying the connection. In this case, it might also be a slippery slope fallacy.
The US has had unmoderated social networks, referred to as pubs, churches, clubs, and town squares, for the last few hundred years. Nazis never gained prominence in any of those fora. It is not a given that reducing the level of moderation leads to Nazis taking over. The truth is that Nazism is such a distasteful ideology that it pretty much never takes over the discourse in places where it is allowed. Rather, Nazis end up creating small hate groups in all sorts of fora, including the heavily-moderated ones (Facebook and Twitter) where they use euphemisms.
Here are a few other sources for you about Nazi communities on mainstream social networks:
I signed up for Gab in 2016 (internet drama voyeurism can be fun), and I got off in 2017. Neo-Nazis on Gab were about as prominent as neo-Nazis on Twitter: a few small neo-Nazi communities existed on both platforms. Gab had a lot of right-wing/pro-Trump users, and was also weirdly Christian, but there weren't many actual neo-Nazis. A platform for right-wingers isn't automatically a social network for Nazis.
The same is true of Voat, by the way. It was started when /r/fatpeoplehate and a bunch of racist subreddits were banned, and it attracted a ton of trolls and mean people, but very few actual Nazis. AFAIK /r/nazi migrated to Voat, so there were some Nazis there, but Voat was not a "social network for Nazis" by any means. Reddit still has many Nazi subreddits with far more users than Voat's Nazi groups at their peak.
I know that /pol/ on 8chan, at least, was full of Nazis and I think it was one of the biggest communities on 8chan. That was a social network for Nazis.
Gab and Voat (as well as other right-wing-focused social networks like Parler) ended up being the target of journalists and left-wing activists because there weren't many people they valued on those platforms, and a lot of people they wanted to hurt. They continue to largely ignore the presence of distasteful communities on Twitter and Facebook (see Jan 6 organizing as a good example of this - it was attributed to Parler, but most of it actually happened on Facebook and Twitter) and put other fora under a microscope to try to find Nazis - particularly if the forum has an overt right-wing bias. The presence of a small community of Nazis is then used to attack and take down the entire platform.
Nazis are on every platform in small, niche communities. They are surprisingly hard to ban. They don't take over platforms no matter how free their speech is. They are shitty people and their ideas are wrong, and everyone knows that.
So, what Voat was full of anti-Jewish slurs for fun?
Is your point that Voat may have been full of jew-hating racists but it's okay because they weren't actual Nazis?
I can't imagine most people caring about making that distinction at all. Except for jew-hating racists who don't want to be associated with Nazis for some reason.
No, that Voat had a small population of jew-hating Nazis, and another small population of racists. It had a large population of fat-shamers and trolls. It was not a "forum for Nazis" by any definition.
If OP had said, "a forum for terrible people," we wouldn't be having this discussion at all, and I would agree with you.
The same distinction I am drawing about Voat is what people routinely say about Facebook, Youtube, Reddit, and Twitter. All of which host far more Nazi content, by the way, than any side-show like Voat.
Toting out the token Nazi groups on a platform to say that every user is a Nazi is disingenuous at best and dangerous at worst.
The US has had unmoderated social networks, referred to as pubs, churches, clubs, and town squares, for the last few hundred years. Nazis never gained prominence in any of those fora. It is not a given that reducing the level of moderation leads to Nazis taking over. The truth is that Nazism is such a distasteful ideology that it pretty much never takes over the discourse in places where it is allowed. Rather, Nazis end up creating small hate groups in all sorts of fora, including the heavily-moderated ones (Facebook and Twitter) where they use euphemisms.
Here are a few other sources for you about Nazi communities on mainstream social networks:
https://abcnews.go.com/Politics/wireStory/neo-nazis-facebook...
https://www.splcenter.org/hatewatch/2021/07/07/we-make-mista...
About the alternate platforms you cited:
I signed up for Gab in 2016 (internet drama voyeurism can be fun), and I got off in 2017. Neo-Nazis on Gab were about as prominent as neo-Nazis on Twitter: a few small neo-Nazi communities existed on both platforms. Gab had a lot of right-wing/pro-Trump users, and was also weirdly Christian, but there weren't many actual neo-Nazis. A platform for right-wingers isn't automatically a social network for Nazis.
The same is true of Voat, by the way. It was started when /r/fatpeoplehate and a bunch of racist subreddits were banned, and it attracted a ton of trolls and mean people, but very few actual Nazis. AFAIK /r/nazi migrated to Voat, so there were some Nazis there, but Voat was not a "social network for Nazis" by any means. Reddit still has many Nazi subreddits with far more users than Voat's Nazi groups at their peak.
I know that /pol/ on 8chan, at least, was full of Nazis and I think it was one of the biggest communities on 8chan. That was a social network for Nazis.
Gab and Voat (as well as other right-wing-focused social networks like Parler) ended up being the target of journalists and left-wing activists because there weren't many people they valued on those platforms, and a lot of people they wanted to hurt. They continue to largely ignore the presence of distasteful communities on Twitter and Facebook (see Jan 6 organizing as a good example of this - it was attributed to Parler, but most of it actually happened on Facebook and Twitter) and put other fora under a microscope to try to find Nazis - particularly if the forum has an overt right-wing bias. The presence of a small community of Nazis is then used to attack and take down the entire platform.
Nazis are on every platform in small, niche communities. They are surprisingly hard to ban. They don't take over platforms no matter how free their speech is. They are shitty people and their ideas are wrong, and everyone knows that.