I don't think this is true... I believe you can declare peace with such a realm, but there will be negative repercussions in your regions. I may not have that right though. It's been a while since I saw anyone try it.
You are correct. Late in the Hammarsett war, I found out that the game mechanics allow you to take back Hatred at severe cost to region stats. I believe you move to plain War, though, not peace.
