What MLK was getting at is that legally allowing people to discriminate - in the eyes of racists - gives legitimacy to their actions, just as the words of Nietzsche and Martin Luther gave legitimacy to the anti-semites of 1930's Germany.
You have to ask yourself which is more important - to protect someone's "right" to discriminate against others, or to protect someone's freedom from discrimination. You can't have both. You can either protect someone's "right" to discriminate, or you can protect someone's freedom from discrimination.
I'd really like to hear your thoughts on that. And as soon as I figure out how to make a poll, I'm going to put that choice there.