They haven't ventured out to kill anyone yet. The National Guard incident? They needed weapons and they needed to get rid of the threat that the soldiers National Guard presented. In that case, I can't argue with the Governor's actions there. The only difference between walkers and National Guard is that walkers have some degree of coordination, after all. There's a ton of reason to what's been shown or implied:Merle was found in a bad state, but obviously someone capable and tough enough to endure what he'd been through. From what we've seen, the Governor's SOP is to fix the wounded and assess their threat status. Merle has been shown to be loyal to Woodbury, which is why he was probably kept around. Andrea has been much the same way, while Michonne was determined to rock the boat and cause chaos.