I never figured out a reason the packs were having troubles, sonhiw does this sound?
Vincent became an elder while the red bloods were taking unwilling slaves, one of which was his pup. He began trying to get the others to attack the red bloods, and after the unwilling slaves were returned, his pup was one of the ones that stayed, and so he is convinced that they did not return all of the forced slaves, and the growing number of wolves that support the attack, are doing so to send the message that they are not to be trifled with. This way Vincent has a personal stake, and the wolves can't just be talked down.