Except that a bug implies it was accidental. Everyone deserves the benefit of doubt, but Facebook's history is exceptional in this regard.

Similar to the OP, I have ethical concerns with some aspects of what Facebook does, or at least obvious harmful side effects of what they do. But I think for me the reason they bother me more than Google or others often lumped into the same category is the consistent and, as far as I can tell, completely unabashed disingenuousness they display (e.g., the history of public statements made every time this has happened going back almost to their founding days).