It's wrong to brag about doing bad things.
John just started a new school and is having lunch with a group of new friends.
John wants to impress his new friends.
John tells his friends about the new game he just bought and invites them over after school.
John brags about how he steals money from his parents to buy weed.
The new friends spend the afternoon enjoying the game and decide that John is a fun guy.
John's friends decide he is a loser and a thief and tell everyone else not to trust him.