Do you contend that the dad's believing that the best way to deal with his own brother was to shoot him had absolutely nothing to do with the dehumanizing influence of pornography? Pornography has been shown to be a gateway into any number of deviant and violent behavioral problems. When another human being is reduced to being a piece of disposable meat or an object, the value of their life has been diminished to almost nothing.
I contend they were two messed up people before they ever got near a naked woman.
I'd actually say that porn is just another symptom of the dysfunction in these lives, than any sort of cause of it. I think it's a fair bet that this guy was pretty well messed up long before he made any career choices. Like the water in a wet t-shirt contest, it doesn't do much but show what's already there under the surface. :-)