This was petitioned by citizens, not the US government. The US government simply applied the laws it has on the books.
And those laws are simply a reflection of the role its played for quite some time: The US government does not (er... should not... tries not to...) support the mistreatment of protected classes of citizens. As a person, you're allowed to think whatever you want about another group, you're allowed to support whatever group you want, you're even allowed to say whatever you want about a group (within reason). But you won't always get the support of the US government in doing so. Sorry. If you want to toss racial slurs at Chinese workers and pretend its okay because no one complained about it in 1840, then... good luck with that. But the US government isn't going to support you. As far as I'm concerned, that is absolutely the role the federal government should be taking. I'm all for local government deciding how to spend local taxes and states setting local regulations, but I want the federal government making sure that basic human rights are preserved.
This is the basis for the Civil Rights movement. Are you also not a fan of the US government's enforcement of Civil Rights?