for forgets sake, PC culture is gonna destroy all entertainment at this rate
shyamalan didn't make this movie because he wanted to show those loving transmissions what for, he wanted to explore the concept of mental illness and make a terrifying movie out of it. yes, there is a stuffty stigma around mental illness and all, and not all mentally ill people are completely deranged lunatics, but you can't ignore the fact that mental illness does prompt people to do such things and that the concept of it can be used for a scary piece of entertainment. besides, it's not like people are gonna walk out of the movie theater thinking "gosh, those transmissions and schizos are probably gonna kill me and steal my children" and anyone who believes that will actually happen as a result of this movie is an idiot.
TL;DR it's a thriller movie, it's meant to be scary, get over it.