Joker does not mock mental disability, it demonstrates it. It is ugly, awkward, sad and lonely. Joaquin Phoenix demonstrates it in a way you cannot deny. Bullying is many times the result of the "imperfect" preyed upon by the socially acceptable. It seems we are either ignorant or numb to it. Our words claim to be against it, but our actions are clearly looking the other way. Arthur Fleck is a "real" person trying to fit in. He has dreams like the rest of us, and he so longs desperately to belong. You go on this journey with Fleck and you feel his pain. You understand his loneliness, and you almost want to route for him. He's a man on the edge and once you push him over, you'll get what you deserve.