Religion, politics, and "Walking in Memphis"

If Union Army = boys in blue, Grant = "blue as a boy can be"

When Memphis fell to the Union Army, they took over one of the Protestant churches as a chapel for the soldiers. The congregation wasn't thrown out -- but the preacher was, and it was made clear that Army chaplains would be conducting the services from then on.

A deacon of the church went to General Grant saying that the congregation couldn't be expected to listen to Northern preachers who disagreed with them politically. Grant said his soldiers couldn't be expected to listen to Southern preachers who were disloyal to the Union. 

(Grant prevailed, and the deacon went on to another subject of interest to him -- the money he had seized on behalf of the Confederate government from Union people in Memphis, only to have it re-seized by the Union Provost Marshall. He said he was afraid the CSA would get after him for the money, and Grant just said he didn't think that would happen while the man stayed in Memphis.)

Apparently North and South had split not only into two countries, but multiple denominations. Was Grant as a non-practicing Methodist aware of this, or did he just learn it on the fly as the war went on?

What about the Catholic soldiers (and there were plenty, with the Irish immigrants and some of the Germans from St. Louis)? Did they have to listen to Southern priests, or were these tossed out of their parishes by the Catholic chaplains? I find it harder to imagine that happening among Catholics than among Protestants -- but I may be way off. Civil wars are strange times.