I wouldn't even say I'm bitter. I just think of the average person and average people in groups as forces is nature. You don't get deeply upset when there's a rainstorm, why get upset when you see horrible people acting horribly? Accepting the reality lets you try and avoid/shelter yourself from its excesses. In this case, that means trying to fill your life and your time with decent people, uncommon as they are; expecting as a baseline basically-evil behavior from large groups of people (govt, social movements) unless the institutions are well-designed; avoiding things like politics where the final judgment is people's unaccountable opinions; and understanding how this manifests in individual behavior when you do have to deal with the average person (eg I have no real interest in fashion, but I dress well because I've noticed how incredibly differently people treat you, a fact that's backed up by what studies have been done).
Regarding your "loathsome vs less loathsome" statement: The key point here is that I know people that are very, very decent, and I've had some success in limiting my close friend group to only people like that.
Eh, that just seems like a matter of where you set your standards. The environment shifted to slightly reduce the barrier to be horrible, revealing which people were below the new waterline. IMO, if all it took to be horrible to others is a little anonymity and/or groupthink, you weren't that decent a person to begin with.
Regarding your "loathsome vs less loathsome" statement: The key point here is that I know people that are very, very decent, and I've had some success in limiting my close friend group to only people like that.