'Divide and Conquer' is a well worn strategy expression. That however, does not in any way  nullify its truthfulness.

It is one of the strategies most effectively employed by those who would rule over us.

They are fully aware that if they can manage to get us fighting amongst ourselves, we are far less likely to notice the gradual curtailment of our liberties and the shrinking of our ability to think and act as best we see fit. 

Manufacturing resentment is one facet of this strategy, and it is working like a charm.