I'm guessing you didn't read the thread.
Years ago, when discussing the humor of Rush Limbaugh, the great columnist Molly Ivins said something that made a lot of sense to me. To paraphrase, she said that the proper target for satire is the powerful. To satirize the powerless, she wrote, is "profoundly vulgar".
I think this puts Bieber (and celebrities with substance abuse issues) in a grey area, someone who has power in the culture who may be at a moment of personal powerless. There needs to be some caution and respect.
What made the Bieber video offensive was that the premsise, by definition, denigrated his humanity. I love animals, but a certain reverence for humanity is essential, We're all unique, but our uniqueness means nothing without our shared humanity. You're a unique expression of a universal truth.