You say that it is moral for government to do, what it is immoral for individuals to do, because of something called "legitimacy".
You say that this "legitimacy" comes about as a function of majority support.
I ask you if this means that it is "legitimate" for the majority to... say... enslave the minority..?
If not, why not?
It's a simple question really. But one which has significant implications if you're willing to address it sincerely.