If people think the nature of the film isn't a reality, then I would direct their skepticism to the true crime case of Adolfo de Jesus Constanzo. I was living in Rio Grande Valley in Texas when that story broke in Matamoros Mexico and everyone was on lockdown for their safety. He was sacrificing children, sometimes the children were deemed unworthy and discarded on the side of the road. Read the case with discretion and caution.
The movie does a good job presenting the subject and though it does use Hollywood effects for dramatic reasons and shock value, it leaves the audience seeing the world differently in comparison to when the film begins.