It first I though it must be the ghost bloods but as has been pointed out they are willing to allow surge binders in their organization as shown at the end of the book when Malaize (or however you spell that) says he wants Shallan to join the Ghostbloods in some split personality way. I thinks it must be one of the groups that thinks the best way to stop the void bringers returning is to kill the surge binders. Can we talk about how ridiculous it is to think that killing the only people who can fight the void bringers would be helpful.