alt Hacker NewsBut is there really a difference? You can can argue that any apparently selfless act is driven by a desire for self-satisfaction, but from an external view the outcome is the same in either case.
You claim that, because for religious believers this desire to help people is driven by faith rather than what you would term self-interest, it's somehow more resolute. But I'm unconvinced that that is the case, nor that people consciously or not, weigh up decisions to care for others in such a calculating manner.
If the divine impetus made you infallibly caring, I would perhaps concede the point, but I haven't see much evidence of that so far.
Right, the desire of religious believers to help others is also self-interest. But the difference is that the expected reward comes from God, not from others. That makes it more resolute, because for the secular person if the cost of the care greatly outweighs the benefit of "common decency", then there is no reason to continue. Whereas, for a religious believer, the benefit of carrying out God's will is immeasurable.
As for your last point - we're all sinners and we're not perfect. The calculation is there, but the individual's faith and/or abilities might be lacking.