I think being upset that someone was greedy because he wouldn't GIVE you something he dropped is greedy. His drop didn't happen because you cleared the map. His drop happened because he was slated to get the drop. It's totally random and odds are that wouldn't have dropped at all if a different person had joined you.

Instead of being disappointed, why not be happy that your friend got an awesome drop? He may have needed the gold to buy something he needs and has been saving up for for weeks.