At some point in our careers, we've all had that one coworker who thought that if they sided enough with the management team and worked as their informant, they would give them a better position and make them the company's CEO.
You're probably going to find out about it anyway, so here's a little preemptive truth-telling: That never happens. Ideally, an employee who flags persistent issues is retained and heard, but often they are either ignored without reward or disciplined for speaking up.
With that, I'm not saying the employee is an unsung hero; I'm simply saying that his efforts won't earn him a raise and management will likely realize he's being too extreme and escalating minor stuff.
Maybe my opinion will be a little too superstitious around this topic, but bear with me. I believe that if you leave people like this to their own fate, they'll eventually encounter the consequences of their actions on their own, without anyone's help. And in this case, I think those consequences will be negative.
Given this situation, would you confront your coworker, escalate the issue to your bosses, or just keep yourself away from the drama at all costs? I would definitely try to discuss it with all coworkers except him (rather than the internet) before arriving at any conclusions.