There is many ways depression creeps into one's life, and absolutely one of those ways is "when things aren't going our way or criticism are made". Things like relationship breakdowns, loss of job, brushes with the law, deaths in the family, are all proven to cause someone to be diagnosed with depression.
I would suspect constant untrue stories being written about you in your workplace, questioning your standing within said workplace, would be another form of trauma that could send one down a dark road.
Have you ever been on the receiving end of lies and rumours about you at work, or in your personal life?? How did that make you feel if so?
How would it have made you feel if those lies and rumours were then splashed across newspapers for days on end, and then a group of strangers talked about you non stop in forums for days and weeks on end? Would it not effect you because you knew it wasn't true, or you didn't know the people,? Or would you just try and ignore it?
Even worse, how would you feel if all of this was happening to someone you care about??
It would be naive to think your words online don't have an impact on someone, just because they are a public figure, and they don't know who you are. They are not a piece of meat. They are human.