Nope, and the Dead Horses are already war-like. The Sorrows are the ones that are relatively peaceful.

Here's the quote from siding with Graham about the Dead Horses:

They remained neutral toward the Sorrows, but as years went on, there were periods of competitive friction, even violence, between the tribes.

And here's the quote about the Sorrows:

The Sorrows' transformation from a peaceful, timid tribe into a merciless, warlike people broke Daniel's heart. Over time, the Sorrows became ever more ruthless in their dealings - even with each other.

Of course it changes a bit depending on whether Salt-Upon-Legs is killed by the courier, spared, or let go. But it's absolutely canon that Sorrows and Dead Horses fight and become more brutal.

I remember something about them preserving their innocence or something

Daniel mourns the loss of their innocence in the Graham ending and that's the only ending that mentions innocence.