No country has the capacity to have law enforcement go on active patrols in the digital space, many fail even to intervene when they're called in.
Platforms need to have some ability to moderate themselves, the things that are sorely lacking is due process in front of an actual court on one side, and some form of international agreement on how to deal with freedom of speech on the other side.
Just take Nazi symbols: it's perfectly legal in the US to fly a Swastika flag on your home, to take a picture of that and to post it on Twitter. In Germany, all three of these acts would be illegal per §86a StGB (with the exception if one was a journalist and tweeted that photo to publicly document this). In other countries, e.g. Russia, flying the rainbow flag may be illegal - something that is perfectly legal and mainstream in Western countries.
Porn is another thing: what is legal in the US under freedom of speech / art, may be illegal in Muslim countries. Not to mention that while porn may be legal in the US, advertisers still don't really want to have their brand appear next to fetish porn.
Should Twitter now ban such accounts worldwide, restrict the availability of the content to certain jurisdictions, should it do nothing?
These are highly relevant problems, which we need to solve as societies of this world.