Sunday Christians will also take anything said about their religion personally, and sometimes as an attack on "their" god. This gives them a false cause and a reason to feel righteous about themselves.
Sunday Christians are very rarely moral or honorable people. They assume that they are good people solely based on their religion, rather than their actions. Sunday Christians are frauds to the religion's bedrock of actual do-gooders.
Insert one of the following: Lie, cheat, steal, blasphem, murder, commit adultery, prejudge, am a racist, etc.
The term "Sunday Christian" is not usable in the example sentence.