Facebook & TV are private endeavors in which participation on the part of both parties is voluntary: they provide a service because they choose to and people consume that service because they choose to. Either party may opt out and seek alternative means of accomplishing their relative goals... right or wrong. If Facebook's community doesn't suit me I can find one that does. If Facebook doesn't like the service they're offering, they can change it.

Hate speech laws would be involuntary. You could not opt out and there would be a threat of force if you should fail to behave as demanded. Worse still... who gets to define what "hate speech" is and when the use of force gets called in?