Does he really say that though?
If that's what he's really saying it makes sense why he'd kill those kids in the cells in Africa...
They stole his comrads lives basically, or what was left of them, they weren't merely conflict diamonds(which is probably what those kids thought they were) with big boss losing grips with himself, and his anger coming to a head... he kills them.
Here's my crappy translations of the dialogue that occurred:
水葬をしない? それで...
[Are we] not doing the water burial? That...
仲間の灰でダイヤモンドを創れ
Turn our comrades' ashes into diamonds
それを俺達は抱いて 戦場へ行く
and we bring them into the battlefield
死してなおも 輝き続ける
Even with death, it will still shines brilliantly
仲間の元で...
The foundation of our comrades
俺達はダイヤモンドドグスだ
We are Diamond Dogs
お前達の無念を海の藻屑にはしない
I won't let your (referring to comrades) regrets drown in the sea
俺は常にお前達とある
I will always be with you all.