Trust. It all came down to trust, a commodity in precariously short supply. An employer seemingly led them to an unprovoked attack, without providing supporting detail. The target begged them to listen to reason. Perhaps it was a trap, it wouldn't have surprised were it so. The situation just didn't appear [i]right[/i], and so he removed Reverin from the equation.  

If it in fact was a trap, reasoned Keystone, he may have just removed their best hope of defense. This would mean that they were all in big trouble. If it was not, then they had little to fear. The only motivation of any importance (except self preservation, of course) was Keystone's promise to his employer, just prior to him squeezing conscious thought from the man. The irony was not overlooked. 

In the span of a second, maybe less, all of these thoughts and more whirled about in the rock-hard orb located anterior to Keystone's neck. Screwed either way, probably by his own choice of action, he doubled down his wager and took a side facing, defensive stance. 

"Harm or alter this man in any way, and I'll have a much more interesting surprise for you, too." 

Trust. It had to start somewhere, even if it was shaky and enforced by threat of violence of uncertain origin. Or, possibly more accurately, [i]in for a penny, in for a pound[/i].