We ought to make an effort in our language to depreciate the use of 'secular' to mean 'atheist', as in 'secular humanist'. It's become something evangelists use to scare their children with. "Be good, or the secular humanists will get you!"
The other meaning of secular is far more valuable - as a truce between religions, including atheism. The acknowledgment that we cannot prove it to anyone else, and therefore will not impose it on anyone else. You can make a moral case for it but the pragmatic case is far stronger: If we force others to adhere to our religion we must first defeat them, and no denomination can be sure of winning a religious war, nor can they be sure that they will always remain on top of the resulting theocracy.
no subject
The other meaning of secular is far more valuable - as a truce between religions, including atheism. The acknowledgment that we cannot prove it to anyone else, and therefore will not impose it on anyone else. You can make a moral case for it but the pragmatic case is far stronger: If we force others to adhere to our religion we must first defeat them, and no denomination can be sure of winning a religious war, nor can they be sure that they will always remain on top of the resulting theocracy.