I think that the usual take on carnal Christians is way off—I‘ve said that. A true believer that is indistinguishable from the world? Poppycock. Very often, they look like godly, righteous people who are teachers of the faith without some sleazy lifestyle.
I think we have Christians all over the spectrum: babes in Christ (from that other post too), those who are maturing in Christ, those who are caught up in a sin (and then perhaps being disciplined). Christians, at any point, can be called “Carnal” when they are being driven by the flesh—but that doesn‘t mean they‘re off committing adultery. Though it might mean they applaud really stupid things when they should know better.
But how do they get there? I mean, what point does a person who is maturing in Christ start being so stupid that they prove they are carnal?