Our Highlander immediately acknowledged the fact that he was facing an former lover of Methos' and boy did he hate the guy at first sight it! The man got all jealous and possessive.

No kidding! It's so obvious that Duncan is jealous as hell! And that Byron and Methos were so doing it. It's canon! Actually, this is one of those times I realised Duncan was really letting his emotions cloud his judgement. Not that Duncan was entirely wrong to kill Byron -- I think even without his jealousy Duncan felt like killing Byron was liking putting down a sick animal -- but he might have hesitated or had second thoughts about fighting a friend of a friend.

Poor Joe. He's the one who hardly ever gets a say in these kinds of debates.