I am here to testify that many devout Christians think secularism, government neutrality regarding religious matters so far as it is practicable, is a very good thing. It's more common among religious minorities in the USA, who are in a position to see that they would be on the short end of the stick of government partiality towards religion; but I've met many Christians in RL who support separation of state and religion. They've been liberal Catholics and mainstream Protestants; and I've not seen any Christian proponents of church/state separation online; but maybe that's because I hang out on an atheist forum.
I'm not anti-Christian. I'm anti-stupid.