@avlcharlie Because "free speech" protects you from government retribution from speech, not private consequences.

In other words, the owner of the space has a free speech right to choose which speech is and isn't allowed on their property.

You have this same right. If I come over to your house, you're free to say "don't talk about religion or you'll be asked to leave." Doing so neither violates my right to free speech, nor makes you liable for the content of my speech, even though you're "selectively filtering" content on your property.

Those rules apply to everyone equally, even social media.