Maybe I'm missing some underlying message, but from I could see its essentially a black comedy poking fun at people with psychosis, which is about as funny as cancer.
If at first you don't succeed, you're not Chuck Norris
I spent last summer going in and out of psychosis, dealing with disassociation and self harming/suicide attempts. I had a total meltdown and lost my job, friends and my home as a result. I thought this was actually a pretty touching and beautiful (if not gruesome due to the subject matter) portrayal of mental health issues. Whilst I never had thoughts or impulses like the murderous ones in the movie, I still related to the disassociatted reality he found himself in. I don't think this was poking fun at psychosis at all. You are quite literally seeing and hearing things which clearly aren't there. When you aren't cowering in fear and confusion, you're laughing at the ludicrous hilarity of it all. It becomes a companion. Not quite a friend but still something you enjoy having around and come to depend on. Because at that point, you've seen so much of yourself that you don't think you could live with your demons. You see happy normal people in the street with their smiles and functional, lives. Their largely uncomplicated minds. And you kinda laugh at them. Mental health issues are terrible. But they also romance you. They pull you in to oppressive holes and you start to like the way they make your lungs hurt. Sure, we've got the dog. The normal, fully functional part of our minds. The part which reasons and acts calmly under pressure. But then we also have the cat. The part of us which likes being reckless. The responsibility shirker. The part which feels everything. The rule breaker. And then I guess there is the man. Who is still a child and can't figure out how their mind works. The part which still has a naive outlook of the world. I think this was an honest and touching insight to the characters psychosis, and not at all offensive. But that's just me.
I saw this movie last night and I liked Jerry. I felt sympathetic to him and didn't think it was portrayed offensively funny to what he was going through, rather what happened was funny, if that makes sense. I wondered if it would offend someone though, but I regarded this more as a story, not a basis to judge his psychosis and people shouldn't form a stereotype. Jerry is just a character who is in a dark comedy, not that the comedy is trying to portray real life. But I think it does create an interest in the subject and people will more likely do their research about it.