I think that comment is OTT and uncalled for. My 11 year old cousin is a Justin Bieber fan, and I can assure you she is not vile and if you met her she wouldnt sicken you. She is a great kid, who loves her dolls, loves her barbies, is lead singer in the church choir and loves Justin Bieber.
Going back 13-14 years I loved the Backsteet Boys, even had a poster of Nick Carter on my wall. And I had no idea who Anne frank was. It doesnt mean anything. Thanks to my dads job I lived in 10 different countries, speak 5 languages, went to the best school in Rome (studied alongside the president's granddaughter, Paganini's son, Ciciolina's daughter to name a few), went to medical school at 17, became a doctor at 22 and like to think I'm good at my job. I didnt take history at school because it didnt interest me and I only found out who Anne Frank was in my late teens. Possibly even more embarassingly I didnt know who Nelson Mandela was until my early twenties
Its embarrassing but it doesnt reflect on my intelligence, my school or how well I do my job. Sometimes things just slip us by.
Someone's husband in the 1st trimester forum didnt know women used toilet paper when they peed until she got pregnant.
Oh and I eventually grew out of my Backstreet Boys phase. Thats all it was a phase which is normal for young teens. In 15 years time Justin Bieber will have faded into the background, and his current fanbase will look back on it and think "i cant believe how much i loved Justin Biber. I was such a silly kid".