Is this necro-ing? If so, sorry, but needed to weigh in.
Speaking as the mother of a tween, I think that what the world forgets is who Justin Biebers target market is. It's tweens. My kiddo loves JB and One Direction and all the other tweeny music. Because it is aimed at and marketed towards tweens. Kiddo has gotten a lot of flak from fellow tweens (usually with older siblings) about her love for JB and 1D, but couldn't care less. I've taught her to love what she loves, and don't like what she doesn't like regardless of whatever "trend" is happening, and she does just that. She doesn't care what kind of music other people like, and can't really understand why anyone cares what kind of music she likes.
In JB's defense as a performer (and not as a human being, as he has displayed some really douchy moves lately), he is really fantastic. I took kiddo to see him perform live in South Africa and the show was really brilliant, I really enjoyed it and I am not a fan of his music at all (and 37 years old.)