We’re talking text here btw, so CP/gore/revenge porn don’t count because those can’t be transmitted over text (links aside).
And if you want to do that as a centralized network, you'll be cancelled by one of services you have to rely on anyways.
I can understand the tendency if there's a business behind it, maybe they don't want the homepage to be filled with polarizing, divisive, or nsfw content etc.
But I do like the idea of letting users decide what they'd like to see other than on the homepage, where I would be Ok with some default filters. Maybe they can be disabled for the inclined.