Exactly, we need a little gate keeping, at least in our tables.
You can choose who you invite to game with, but it's not your responsibility to choose who does or does not participate in the hobby. If you don't want to have discussions with them, nobody is forcing you to.
The quoted post from the reddit is asking to examine an aspect of the game - who is 'kill on sight' and what that means for the game. Maybe there's a better way; maybe thinking about it is worthwhile.
One valid criticism of a lot of 'evil' is that they don't do anything that the good guys don't do; there is team ugly and team pretty, and basically they treat each other the same if they're in charge. When I want my players to know who the bad guy is, I want him to do something deplorable. In a TV show, you let the bad guy kick a puppy (or kill John Wick's dog) so it's clear that he is a bad guy and nobody has to feel guilty about taking him out. From my perspective, that's the LEAST you can do in your games. If the bad guys do bad things, you don't have to ever worry about whether
you're the bad guy because you're kicking down his door and taking all his booty.