Make no mistake, there is definitely a time when hating the Justin Biebers and David Cassidys (ask your mom) of the world is perfectly acceptable. That time is when you're a young male in the 10- to 16-year-old range. That's when a man starts to take an interest in girls, which means he's moments away from finding out that most of those girls, in turn, have taken an interest in Justin Bieber (or their respective decade's equivalent). At that tender young age, Justin and his slick dance moves and somehow baggy yet also skinny jeans make him the ideal version of a man in the eyes of most of the chicks that young dudes are trying to get awkward with.
And in the eyes of men that young dudes should try to avoid.
Those gentlemen get to hate Bieber. They are fighting for territory on the same battlefield and he is beating every single one of them soundly. He is the enemy.
Once you've outgrown that awkward period in life, though, you are allowed approximately three more circumstances under which you can be angry at a teen pop sensation. Those are as follows:
1. You're a parent who's forced to listen to shitty music because kids don't know any better than to have awful taste in everything.
2. You work at an establishment (bar, restaurant, brothel) that plays background music you have no control over.