Nowhere. It always puzzles me why this response always crops up, even when I never even remotely try to claim that platforms have any legal obligation to host content.
I did claim that making their site have a partisan recommendation algorithm is not a good idea and may be bad for society. I have zero doubt that this is their right, but people and companies have the right to do plenty of things that aren't good for society. Saying that it's bad for society to implement a partisan recommendation algorithm is not at all the same thing as saying it is or should be illegal.
My theory of HN comments: People prefer to respond to familar arguments, rather than the arguments you make in your comments. People prefer to discuss topics that they are familiar or passionate about, rather than the specific topics addressed in the articles or parent comments.
Posting Fast and Slow
So who gets to decide what is good and bad for society?
It's entirely valid to say that tech companies' censorship or forms of manipulating views is bad while acknowledging that this is their legal right. This comment applies just as much to you: https://news.ycombinator.com/item?id=19525998
Everyone does. Everyone makes their own decisions about what is right or wrong.