Here's my .2 cents as to why NH invites so much negative attention -
First of all, by segregating themselves from other horseman by calling themselves "Natural Horseman", thereby implying the rest of us are unnatural.
By making it seem like "natural horsemanship" is something special, separate and apart rather than just the principles of good horsmanship. Understanding the horse's body language and herd behavior, training without pain or fear and using pressure and release have been around since Xenophon, and good trainers have been using them since then. Why the need to brand it as something new?
The PT Barnum type marketing approach and product branding of some of the current NH gurus.
The exploititive nature of some of the NH trainers that has lead many novices to believe that they can learn to train horses from watching DVDs.
To sum up, I find the principles of the so called "NH" to be interesting and useful tools for any trainer's tool box. I find some of the current NH trainers to be very interesting, well worth watching and learning from, and incorporate some of their ideas into my own work with horses.
I find the business and marketing phenomenon known as Natural Horsemanship to be ridiculous and some times dangerous.
So that's "what's with all the haters."