There are also misguided notions that being the defender in a war should allow one to completely bypass warmonger penalties
Not true, there is a difference between allowable reaction and being an actual warmonger. Normal spoils of war (capturing territory and/or cities) being "warmongering" is a very modern way of thinking that poisons the games' logic, it's a kind of thinking thats only about 100 years old and this is a game that spans mellenia. Warmongering should be for agresssive action not reaction.