Very well said. I have seen firsthand what evil is and most gamers don't come close in their interpretation of evil, much like you described as expected from your gm.
Evil is a spectrum.
It's not like you move from CN one step too far and suddenly you are Demogorgon.
Playing CE character does not mean playing PURE EVIL, just like playing LG does not mean playing Jesus Christ.
I play with CE rogue in my team and NG archer, and it's working, because archer girl is not self-righteous, and rogue is not murdering psychopath, just you know amoral thief.
Wouldn't it be better if we just left the politics out of gaming and just gamed for fun?
No. Gaming is cultural activity and culture is and always was inevitably tied to politics and vice versa.
Also being conservative and liberal is not just political stance, but also philosophical, ethical and so on.
You can pretend you ignore it - but even then unconcioussly you're taking some stances.
Problem is SJWs are insufferably nagging about it