On its own not much at all but when taught as part of his training it reinforces the dangerous notion that the police are better than the citizens they serve. All from an 'expert' on combat who has seen none himself, even I have seen more 'combat' than he has and that ain't saying much at all.
WRT
Sheepdog and Grossman's training (that I have observed and read), you couldn't be farther from the truth. He absolutely does not teach or condone the notion cops are better than citizens. Again, if some folks, like you, get the idea that is something
Sheepdog teaches without proper research or context, he can't help that. Get more information, make inquires, read more of his stuff, attend a lecture or training he is giving.
Grossman is not an expert on combat as in tactics, and never asserts that. Never lectures on it or written on tactics. As a psychologist, he is an expert on the psychological aspects and affects of violence and by extension, combat.
For some deeper analysis of the Sheep / Sheepdog meme, pick up
Tom Ricks' Making the Corps. This recommendation is not a shot at the Marine Corps, but instead an opportunity look at how and where the transformation from civilian to somthing-better-than-civilian begins to takes place.
As an aside, what's the correlation between those who strongly subscribe to Sheep/Sheepdog philosophy and those that have MOLON LABE decals/tattoos/t-shirts? That's not snark. That's a real question based on understandings (misunderstandings?) of history and soldier's roles as citizens.
I haven't read
Making of the Corps. Grossman has made dozens of presentations to USMC and US Army units in predeployment training. From his descriptions, his lectures to those audiences is more about surviving the psychological aspects of combat then something like
Sheepdog and their place in civilian society. But to your point, just like viewing your enemy as evil and sub human ( taught to soldiers from the dawn of organized combat) helps a soldier deal with the killing of another human, even if enemy, having a soldier see himself as something better than civilians triggers an almost parental protective notion that helps them deal with the sacrifices they are making. Taken to an extreme, yes the better than civilian attitude can be harmful. But so can the enemy as sub human and training men to look through a scope, pull a trigger and blow a head up like a melon. Yet the military does a pretty damn good job of balancing all that with basic humanity and civility.
As to your final question regarding correlations, I'd say about the same as the dude you pass on the street with tattoos and a convict.