About Kant:
There used to be a comic strip in the US, called "Li'l Abner" telling stories of a bunch of rural folk we call 'hillbillies'. Abner Yokum's mother was a wise little woman who used to say "Good is better'n evil, 'cause it's nicer."
Kant spent many pages in turgid German saying essentially the same thing, but 'proving it' with complex philosophical language, which included stuff we would recognize as essentially "The Golden Rule". You might 'guess' that the Yokum family were Christian, but such was never mentioned and it just seemed like a good idea when Mammy Yokum said it.
   Many religions have a version of The Golden Rule, and of many other ideas of right and virtue similar to what is found in Christian teachings....Kant just tried to explain WHY almost everyone who thought much about it decided that 'goodness' was a sane, reasonable path, whether any Prophet or "god" told us so or not.

   Today, there are atheists who behave in a sane, fair, honest, loving manner towards others...without needing to be 'threatened' with eternal punishment.... and thus, they don't appreciate being threatened with eternal punishment for not 'believing in Jesus & the bible', when they are living good lives already.

   Most atheists treat all the layers of theological complication about 'original sin'...etc... as stories created to convince and scare people who can't comprehend Kant's...and Mammy Yokum's... basic idea.

That's the best I can do as a quick summary.