mental illness has a stigma, which in the last few years, slowly has been fading, however, it's still very easy to put people back into believing the stigma. Movies like this, while it is not their goal, help bring the stigma back. People who suffer from that have the right to complain about it. I get that making a horror movie with the lead antagonist being a scary person with motives you don't understand as they come from a mentally insane mind is an interesting watch, but a lot of people will forget that it is an overexaggerated movie and will portray that overexaggeration onto a normal person who suffers from a mental illness in real life.
it is a pretty big mess a lot of people have been trying to solve, but no matter what people come up with to prevent the stigma, nobody wins.