I think the argument here is guilt by association.

It's a bit like banning entry into the US because you've visited Russia.

It doesn't really matter how Russia runs their own country, you might have even gone there to argue against totalitarian dictatorships.

But a US border guard looking at your passport and rejecting your entry based on that alone feels like overreach.

How subs choose to moderate their content is roughly speaking sort of fine, as long as there's no organised harassment, sharing of illegal materials (child porn, revenge porn, war materials etc) and threats of violence or death.