For contrast, YouTube was knowingly and illegally hosting pirated content for years before Google bought them and developed ContentID, and relied entirely on volunteer moderation (user flags) to detect it. Facebook has up until very recently relied entirely on user flags for moderation. Google web search is theoretically entirely unmoderated. And so on.
Valley firms built their financial success on being content neutral and even turning a blind eye to blatantly illegal content until they found ways to automate enforcement (or not), but are now forbidding competitors from being the same.
You don't recall Parler doing that either, because they didn't.
Now if you compare apples with apples, can you recall people using Google to research how to do bad things? Sure. Plenty of people who went to prison after police found they'd been searching for stuff like "how to hide a body" or bomb making instructions.
Valley firms built their financial success on being content neutral and even turning a blind eye to blatantly illegal content until they found ways to automate enforcement (or not), but are now forbidding competitors from being the same.