Of course it doesn't show up: most if not all Mastodon servers ban you for having the wrong political ideology, it's in the server rules of most of them.
As an example, that one will ban extreme (and not so extreme) right-wingers. But you also have the opposite in other servers. And of course those servers refuse to federate with others. So there obviously are no flame wars like on Twitter... All ideologies are separated.
The reason there are no flame wars is not that Mastodon users are somewhat enlightened, as opposed to the Twitter rabble. Instead, clashes are avoided by having (and enforcing) rules and banning ideologies. The catch here is that this would never scale; this only works because there are only a few users.
I tried following https://pl.smuglo.li/users/roka (an anti-Semite who posts porn) and got a nondescript error. How can I tell if this is due to a blacklist, and if so, if it's on my instance or theirs?
In any case, you should contact the admins of your instance, but most probably they have blocked that instance, as it appears on blocklists for being a free speech zone.
It's the default, and most instances stick with it. None of the items seem controversial. Which one stands out as a problem to you?