I know why a lot of people see it as problematic (white beauty standards and all that). However, I don't see why anyone SHOULD have a problem with it. Mind your own business. If someone wants to bleach their skin or be lighter for whatever reason, that should be nothing to you. Let them do what they want to make themselves happy.
I also can't really blame dark people for wanting to have lighter skin. If you're going to blame anyone, blame society for causing dark people to feel like it's NECESSARY for them to have lighter skin in order to fit in, or be treated equally to light/white people. The problem starts with euro-centric beauty standards being pushed as the be-all, end all. The more we promote strong, intelligent, beautiful and powerful dark-skinned people in the media, the more effective we will become at eliminating peoples' NEED to skin bleach.
I actually feel more sympathy for dark people that bleach because I understand why they feel the need. Aside from the harmful effect it has on your body (which is only true when using the wrong type of product), it's really not your place to judge them. Instead try to understand where they're coming from, and do a better job of making them and others like them feel loved just the way they are.
It's really the only thing I sympathize with Azealia about.