There is some truth in what you say, just like saying you're a "free speech absolutist" sounds good at first blush. But the real world is more complicated, and the provider adds safety features because they have to operate in the real world and not just make superficial arguments about how things should work.

Yes, they are protecting themselves from lawsuits, but they are also protecting other people. Preventing people asking for specific celebrities (or children) having sex is for their benefit too.