Blocking "controversial" things is cheaper for social media companies than keeping them up (most of the times); they're not in the business of making a fair and enjoyable platform. They're in the business of selling you: useless subscriptions, paid propaganda, items you once searched but have no interest in or have already bought recently, questionable financial/legal services and of course everything else that would make them even slightly more money.
It's not like Facebook actively wants to choose the things that should be banned, they really do not care. It's just that their analysis shows that they could make more money blocking a few nipples because advertisers will pay more on average, and given the choice a company will chose profit over the wellbeing of their product.
I actually like the EU clamping down on internet companies (although it's far from perfect, to say the least). Companies shouldn't have so much power over society they should be controlled by society or they will just spiral towards money like a paperclip factory AI spiralling towards paperclips.
Why should it be fair that a newspaper is responsible for the public letters and ads they publish, but Facebook should not be responsible for the public's messages and ads they publish just because they don't print on paper but use the internet?
If a company makes money off public content, the company should be liable for it.
You can't have your cake and eat it too.
Finally, it's not about people "volunteering" to abide by rules of a social media company.
If it would be about the user, they would just make a setting and let the users choose for themselves what they do and do not want to see.
It is in fact about advertisers dictating rules and internet companies seeing nothing in their way from screwing over their users in order to make more money.
We've seen this before, companies screwing people over to make money when there are no/weak regulations.
The internet should be free, but companies generating revenue from it should be regulated.