I think Greenies make dogs evil. My Malt was really bad with them.. he would growl at me whenever I tried to take the Greenies away from him. My solution was to take them away from him every couple of minutes. I kept doing that every time he would eat them. He is better about letting me take them away from him.. he won't growl at me, but he is still protective of them. My biggest problem now is that when I try to take them away from him he'll try to eat it really fast before I can grab it. He downed a huge chunk yesterday and ended up puking it up this morning.
I think I might have to not let him eat them anymore after that little scare.