I always try to remind myself that my parents were both products of their times and (their own familial) upbringing.
I can still experience the trauma of ways in which they've hurt me in the past...but it's also vital, for my own mental health, to remind myself how they have actually changed since those days.
I can feel bitter about things that happened to me as a kid and teenager...but the only value to that emotion is if I harness it to determine how I'm going to use those experiences to make a difference for OTHERS in the future (so they won't have to go through what I went through).
The real problematic people out there are the ones who intentionally refuse to change, regardless of the feedback and hard truths they receive from those around them.