Say what you will:
The Diamonds, the former "villains" of the show, were more like family to Steven than the "heroes" of the show, the CGs.
Yes, I know what each of them have put him through. We all remember Change Your Mind and what White did. And by no means am I saying that any of them are excused or deserve to be forgiven right away.
In fact, Rebecca herself confirmed that Steven himself hasn't forgiven the Diamonds:
And Steven's feelings are valid in this. He has every reason not to forgive them.
But if I'm being honest? The Diamonds treated him more like family than the CGs did.
Remember: Steven willingly went to them in "Homeworld Bound" and they were more than willing to help him, even if their advice wasn't the best. And Steven was willing to at least try it and things were going good until his PTSD from CYM almost caused him to shatter White.
But when you really break it down, the Diamonds treated Steven more like family than the Gems ever did.