Trust and everything else

I got backstabbed in my company.
I know who it is. And I won't plan on any vengeance. It would be a waste of time.
How people think and how they act on their thoughts is something you can never control.
I supposed he felt threatened the day I joined the company. Leapfrogged over him to take over 2 departments.
He's 15 years my senior and had been serving in the company for 10 years. Perhaps he thought he was the most eligible candidate to take over the post.
To laugh at me while I was reprimanded by my directors was an evil thing to do.
I cannot fathom how anyone can keep so much venom in themselves. Is it worthwhile to keep all that poison in your heart, like a cancer slowly eating you from the inside?
I still acknowledge him. "Good morning" etc. But he'll never talk back to me. Weirdo.
All I can think of is this phrase.

Be kinder than necessary, for everyone you meet is fighting some kind of battle.

You can meet nasty people, impolite ones and absolutely horrible persons with no notion of what manners mean.
It does not mean you have to be a bastard/asshole back at them. I can't remember, but maybe it was Gandhi who said you can win over your bitterest enemies if you give them sufficient love and kindness.
Everyone has their own inner demons. That they're fighting off everyday. In their minds. In their hearts.
I believe in the goodness of humans. I trust that everyone has a good side to them. Nevermind any bad side.
To be able trust your fellow human, I feel, I suppose that's the biggest hurdle for most people to overcome.
But without trust, there's nothing else.