Do not anger the Beliebers.
It's a lesson that's inherent to those who report celebrity gossip, but one Olivia Wilde had to find out the hard way after chastising the singer on Twitter.
After Wilde told Justin Bieber to "put a f--king shirt on" earlier this month, her account was bombarded with irate messages from riled up Beliebers.
Very intelligent and totally sensible ones, obviously. Watch below as the actress reads some of the best Tweets she received on the Tonight Show ...
Wilde also offered a preface: "This started because Justin Bieber went out without his shirt on… he was in London, and it's so cold there and I was concerned."