I waited until my employee donated bone marrow for someone I know before passing him over for a promotion
That doesn't sound right. Did getting a promotion mean a lot to him?
Promotion means a lot to him, I know him well. I don't need a skilled employee if he is going to leave anytime soon.
It sounds like you took advantage of your employee. That is incredibly rude and insulting.
Look, the man knows my decision is final.
It was still wrong to wait until he donated the bone marrow to turn him down for the promotion. He likely did that favor thinking you would return it with the promotion. You should have been more upfront than that.