No one respects a disloyal friend.
Greg was hanging out with his friends at the mall when a popular jock asked him to come with his friends instead.
Greg has to pick who he wants to hang out with.
Greg tells the jocks that he's hanging out with his friends, so he's not leaving.
Greg decides to hang out with the jocks and leaves his friends.
Greg's friends feel better about Greg and trust him more.
Greg's friends feel betrayed and don't like him as much as they used to.