Everyone should be offended when the US government supports religion in any way. Everyone. Even if it is supporting your own religion. No one should be happy to see the Ten commandments posted in a government building, for example. Why? Because nothing lasts forever, including your stranglehold on the religious of the majority of Americans.
What if tomorrow, a significant proportion of Christians decided that your god had sent a new prophet. And what if this prophet said that you've all been doing everything wrong, and must convert to Islam at once? Don't tell me it couldn't happen. If gods can send prophets to ignorant, superstitious desert tribes, they should be able to send prophets to modern people, right? Shouldn't they? Or can't the god(s) do that sort of thing anymore? If not, why not?
So say this prophet gets 60 percent of Christians to convert to Islam. Now they're going to go rip down all the Judeo-Christian crap you've posted everywhere and replacing it with Koranic teachings and Sharia law. Are you still ok with majority religion being slapped all over the government?
What if it wasn't Islam? In fact, what if it wasn't an Abrahamic religion at all? What if the sky opened up tomorrow, and the goddess Diana appeared from above? What if voices in the yearly California brush fires told firefighters that they'd better start worshiping the Hindu gods or they would end the world?
The truth is that you can't count on your religion always being the majority. And if you disapprove of someone else's religion being splattered all over the government, they why is it ok when it's yours?
Or maybe you're just pining away for an Evangelical theocracy. In which case, not only does religion get involved in the government, but now the government is getting involved in your religion. Do you really want that? You don't trust them to provide you with free health care, but you want them messing around in your religion? How does that make any sense?