I think his grievances may be as much made up as not.
But then, all I "know" about the situation is what the Media say.
Consider that the mass media have handled Waco, Gordon Kahl, and Ruby Ridge with such unbiased fairness, and it almost makes you wonder.
Those raised on violent video games and gangsta rap will likely see someone 'heroic', getting back at "the man".
The difference is that Dorner is on the same side of the ideological fence as the media.