I tend to judge the actions of others, even fictional others, based upon how i believe i would react in the same situation. Not society overall, just myself. Period!
See, regardless of what society's rules may suggest and attempt to control, we humans are not all that civilised and the more we pretend that we are, the more the opposite tends to happen. In other words, as human society attempts to repress it's animal nature, that same nature is fighting it's way back to the surface and becoming all the more violent because humanity has been trying to surpress it for so long that we are forgetting how to control it. You ever ask yourself why violent crime is on the increase and why there are more serial killers and psychos on the streets now than ever before? The answer is simple. Humanity has been trying to ignore it's origins for too long. Deep down inside we are animals, people, live with it!
Okay, what does all that have to do with the thread topic? Well, everything, really. The basic question is whether what Wes did was wrong, and judges by society's laws and rules, of course it was. But judged by me? Not wrong at all! Wes did exactly what was required, both for him and for the mission at hand. No namby pampy, boohooing about right and wrong, just a pure, instinctual reaction to the problem in front of him.
Wes avenged the woman he loved and in doing so he removed a potential threat to himself and his friends. Was it murder? Yep! Was that wrong? Not in my opinion because, believe me, if somebody ever ritualistically sacrificed somebody i loved i would do exactly the same thing and to hell with society. Sometimes the most just thing a person can do is listen to his or her most primal instincts because that is where true justice lives.