As a Christian, I was raised on the concept of the golden rule–that you should treat others as you would like to be treated. And as a Mormon, I believe in the reality that all of humankind are brothers and sisters, children of the same Heavenly Parents, and that we lived together before this mortal life.
As such, I also believe that all of us will someday stand before our Maker with our memories of our pre-mortal life restored, and we’ll see again that all of these people who’ve been around us our whole lives really were our brothers and sisters and friends, regardless of where they were born, what color their skin is, whether or not they lived in accordance with our understanding of the gospel, whether they agreed with us politically, etc. And in addition to remembering them and our past friendships, we’ll also have a perfect knowledge of how we treated or mistreated them.
I think a non-trivial part of hell will be the shame of realizing that the people who we were mistreating, demonizing, bullying, despising, hurting, and rejecting were people we knew and loved before this world, and yet we had been monsters to them. On the flip side, I think a non-trivial part of heaven will be the joy of realizing that those people we helped, and comforted, and strengthened, and forgave, even if we thought they were total strangers that we would never meet again, were in reality really dear friends long forgotten.
I’m far from perfect at consistently applying this belief. I still get angry at other people, I’m not always kind or forgiving. I’m often quick to impute negative or dishonest motives to people I disagree with. But I still believe with all my heart in the reality of the brotherhood/sisterhood of humankind.
You’ve never met a true stranger. Only family.