Was Petersen right?

When Petersen admitted to the killing of Waters, his simple reason was that 'some things need getting rid of,' I personally would never have condoned killing such a man regardless of his despicable character, but do you think that to an extent he was justified in murdering Waters under the circumstances in which his company was being mistreated by their own commanding officer?

I do understand the anger and frustration that Petersen was going through, and probably most men in the company felt the same way too (except of course that kiss-ass Wilkie), but my own conviction is that it probably would have been a wiser idea for Petersen to just let Waters be and continue going down his drunken binge, given Water's deteriorating emotional and mental condition, he would have eventually been deemed unfit by the Army to command his company, therefore preventing him from ever mistreating his own men again.