A lot depends on who is saying that.
A now deceased family member used to insist that "he's a good Christian man" when my wife and I tried to point out to her that someone was taking advantage of her. A tradesman charging top dollar for work I could see without even measuring wasn't straight but she refused to listen because "he's a good Christian man". She used the same words to describe her preferred politicians, refusing to accept they were doing anything other than exactly what was right for her and for the world. So when she described someone as "a good Christian man" I figured that person was probably some kind of con artist.
