Would you be upset if a friend told you?

Would you be upset if a friend told you that your child had major behavioral issues? The reason i ask is because this week i offered to help a friend and watch her 4 year old while she went on a trip. Well this kid is in need of discipline major discipline. I don't even know how to handle him. He's always crying and screaming and fighting. He actually bit me when i tried to make him sit for dinner. I've known him his whole life so its not like i'm a stranger. I've always known he was a little rambunctious but i guess i never noticed how bad it was because i've never had to deal with him in such a concentrated dose. I have no idea how to handle it i feel like i might be overstepping my boundaries if i discipline him and i don't know how to bring it up with her. She dotes on him and in her eyes he can do no wrong. Should i just count the hours until he's gone or speak up?