Merely being content-based doesn't imply unconstitutional. The CAN-SPAM Act, for example, is content based. This would be similar to that: allowing immunity for

Merely being content-based doesn't imply unconstitutional. The CAN-SPAM Act, for example, is content based. This would be similar to that: allowing immunity for moderation of commercial speech, obscenity, etc while holding companies accountable for moderation of most speech. And that is protecting the free speech rights of users, in an age when the public space is controlled by private corporations, so there's a compelling government interest involved.