The Canadian pop star was taking a beating online Sunday for a note that the Anne Frank House in Amsterdam said he left in its guestbook after touring the museum with his entourage for more than an hour on Friday.
On its Facebook page, the museum said Bieber wrote he hoped Frank "would have been a Belieber," the nickname embraced by his fans.
The comment sparked outrage on Facebook, with many accusing the 19-year-old crooner of being disrespectful and ignorant.
Some Twitter users took a more lighthearted tone, listing other historical figures — including Abraham Lincoln and Helen Keller — who might have been fans under the hashtag #wouldhavebeenbeliebers.
Frank was a Jewish teenager who kept a diary while hiding from Nazi occupiers during the Second World War. She died in a concentration camp.
Her diary has become the most widely read document to emerge from the Holocaust.
Museum spokeswoman Maatje Mostart confirmed Sunday that Bieber visited Friday evening.
She said the museum was happy to have received Bieber and didn't see anything offensive in his remarks. She said he called ahead and was given a guided tour.
"Truly inspiring to be able to come here. Anne was a great girl. Hopefully she would have been a belieber," the museum said he wrote.
"That little idiot is way too full of himself. She's an important historical figure so show some respect," one commenter wrote.
"What a immature and disgusting thing to write in her book!" read another message.
Others came to Bieber's defence, saying he should be commended for trying to learn about Frank and likely meant to say he would be proud to count her among his supporters.
A source from Bieber's camp said the young star meant "that it would have been an honour if she had been a fan" and that the visit was a positive, educational experience.
The Centre for Israel and Jewish Affairs, a Canadian advocacy group, declined to comment on the incident, and other groups could not immediately be reached Sunday.
The singer has made waves in recent weeks, stirring drama both on and off the stage with bizarre fashion choices, outbursts, and concert disruptions.
In one instance last month, the teen heartthrob was forced to leave a monkey in quarantine after German authorities said he didn't have the proper paperwork to take the animal into the country.
His tour has him booked with shows through August.
--With files from The Associated Press