From Working With McKinsey:
If your McKinsey boss knows that you disagree with something, you will be reminded of your “obligation to dissent“. “Dissent” is a strong word, but in this context it simply means speaking up if you disagree with something being done or discussed.
The “obligation” comes from the fact that at McKinsey, voicing your dissent is not optional, it is required.
The Firm believes that every consultant – even the least-tenured, greenest Business Analysts and Associates – is intelligent and has valuable insights to offer. On McKinsey engagement teams and in collaborative problem solving sessions, everyone is supposed to have an equal voice and is expected to contribute to discussions – that includes exercising the obligation to dissent.