Just saw the movie tonight. I wish I hadn't.
I voted yes. While the acting is ok - though the main character overplayed his role - this is an extremely dark, depressing movie that tries to portray the "Joker" as both sympathetic and cool - as he became a mentally ill, psychotic murderer. You won't leave this movie feeling good.
I voted it is dangerous for a specific reason. Subliminal suggestions are extremely powerful on people - with this understood in the movie industry. DOZENS of times in the background they had signs and newspaper headlines declaring "KILL THE RICH"! (rich people), portraying wealthy people as arrogant, cruel and aloft, while everyone else was desperately poor, barely surviving, because of the rich people. All wealthy characters of any significance in the movie were evil, viciously violent people. It also blames him becoming the Joker for lack of social services money - also the fault of rich people.
Basically, the underlying theme of the movie is that evil greedy and violent rich people created the Joker - as they destroy society - and lead to everyone who isn't rich being a desperate victim. In the end there are poor-people riots murdering police and wealthy people in a semi-heroic sense - while flashing "Kill the Rich" over and over and over as background subliminal suggestions. Bruce Wayne (the future Batman) is a child - and his father is portrayed as a violently evil man, with him and the mother murdered by someone motivated by Joker's righteous murders of 3 rich guys who were beating him up just because they were rich and therefore evil.
Joker is portrayed as a hero to the poor people because he is murdering rich people. Basically, that is the entire subliminal suggestions and theme of the movie: All rich people - meaning everyone who isn't very poor - are the cause of all problems and therefore they all should be murdered. Joker, despite all his efforts to devoting his life to making people laugh and be happy, is forced systematically by evil rich people to justifiably become an insane psychotic mass murderer.
I voted yes, though it has nothing to do with portraying violence itself.