Usually appears in the context of Affirmative Action. If under-represented minorities and women are given "special consideration," such consideration is at the cost of blameless and innocent whites / males who cannot benefit from this consideration. This differential treatment constitutes "reverse discrimination"
(Minor form: Liberals discriminate against republicans... specifically, Ann Coulter.)
I heard a debate involving Ann Coulter. She blamed liberals for making it hard to get her books published. I wished for the response to be: "Liberals" are no unified group. As Will Rogers once said, "I don't belong to any organized political party. I'm a Democrat." If you had any problems, Anne, it was because of taste, not some cabal of liberal publishers.
At the heart of this is the ignorance of "unearned privilege," which is extremely difficult for privileged folk to acknowledge. Peggy McIntosh of Wellesley College has some excellent articles designed to help people acquaint themselves with unearned privilege. Notable is her essay the invisible knapsack