"Is he just angry at everyone?"

He is irrationally distraught, to the point of advocating violence.

The reason this piece works (for me) is that everybody is irrationally distraught at this time in their life. So while I get that he wants pain and suffering inflicted on those he views as responsible for his dad's suffering, I could line up a million more people who want to cling onto dear grandpa as long as the old guy has a breath. Everybody is irrational and emotional at this time. That's the nature of the phase of your life that involves burying people you love. And it's the exact reason that others behave in ways he finds abhorrent.