Excellent example: in the early days of Reddit, they very much had a "you can post anything that is not illegal" policy, and this led to subreddits like jailbait, fatpeoplehate, etc. Around 2012 I think (someone can look up the exact date) there was a coordinated effort to shine a bright media spotlight on the "underbelly" subreddits that made a ton of Internet and national news, e.g. features by Anderson Cooper on CNN, prominent op eds in NY Times, etc. Reddit changed course and specifically banned sexually suggestive pictures of minors and those without consent.
I have an opinion, but I am not arguing here for whether the decision was "right" or "wrong". I am simply pointing out that Reddit had 0 choice in the matter. If they had held firm with their "anything that's legal" policy, they would simply not exist today. They would have been deplatformed to the nth degree, and furthermore laws would have (and actually have, e.g. in the case of revenge porn) changed to make their existence untenable. E.g. platforms like Reddit can't exist without Section 230, which is already under attack and I guarantee would have been removed if you had lots of platforms saying they're fine with people posting unknown, sexually suggestive pictures of minors. Nevermind having 0 advertisers willing to pay their bills.
I'm not crazy about "SV moral arbiters" either, but I don't like posts like yours because they pretend a reality that doesn't exist.