@AviK
Congress could pass a law that online forums were public forums, but it would lose a Constitutional challenge. Fairness Doctrine only applied to public airwaves and TV stations are licensed to operate at those frequencies for X years at a time.
First Amendment rights cannot be applied to private business, unless they are acting in the government’s place. So if the Government rents space for a Post Office or Social Security office, the private landlord can’t ban Jews or Muslims from coming in the property, or distribution of literature on the sidewalk leading in, or other Free Speech protests