Its like being angry at Signal because their encryption allows terrorists communicate securely.
(There are lots of anecdotes of individual users who get temporary bans on Twitter for political speech, but I have heard those anecdotes across the political spectrum. I suspect conservatives grumpy at Twitter would be very surprised how much left-wing discourse there is about how Twitter protects TERFs, how they pay lip service to banning Nazis but don't really do it, how Jack Dorsey is probably a crypto-fascist, and so on. The parallel -- "I know of people who agree with me who have been moderated and people who disagree with me who have not, ergo Twitter is obviously biased in favor of The Other Side" -- is kind of fascinating.)
Most of it could also be posted on Twitter and Facebook, although there it might get labeled as misinformation.
It's actually fairly difficult for the overwhelming majority of people to get legitimately kicked off of most mainstream social media. By "legitimately" I mean by actually violating the site's published rules. At the scale of these sites there are occasional mistakes made where someone gets banned who shouldn't, and it can be difficult to get that reviewed, but nevertheless for most people those sites are "free speech social networks".
Because of this, when you start a site like Parler you get almost all of your initial membership from those people who got kicked off of Reddit, Twitter, etc., or who are having to work at not getting kicked off because they want to post calls to violence, etc.
That sets the tone for the site from then on. Hence, when a site is specifically selling itself as a "free speech social network" it almost always can correctly be interpreted as "a social network for <X> extremists who could not follow basic norms for civilized discourse" for some X.
Can you name a "free speech social network" that isn't overrun by white supremacists and Nazis?
It turns out that if you prioritize free speech, then the people who congregate on your site are mostly those with beliefs that are sufficiently repugnant that decent humans don't want to be associated with them.
Much like, for example, the gadsden flag.
"if a working interface is only for bad games, I fear what good games look like"
Good games have working interfaces too, but they have a lot more worth talking about.