Seriously, when I saw the scene it felt like I hadn't watched carefully the previous times because it looks SO obvious! Instant dislike of the man for reasons that seem to need no explanation and an outcome that can't not have something to do with Methos. I'm like you, I think that Duncan did have reasons to kill Byron --we're talking about Duncan MacLeod of the clan MacLeod after all-- but I can't shake the feeling that there was more to his behaviour than meet the eyes.