"Either we accept this proposal or we do nothing." "You're either with us or against us." The structure is always the same: a landscape of possibilities is compressed into two, one is made unpalatable, and you are invited to accept the other by elimination. The reasoning would be valid if the two options really were exhaustive. Usually they are not, and the whole argument rests on that concealment.
What makes the false dilemma unusually powerful is that it does not feel like a trick. Binary framing feels like clarity — it cuts through complexity, it sounds decisive, and it hands you a clean decision in place of an uncomfortable mess. Ambiguity is cognitively expensive, so an argument that removes it is welcome even when what it removed was the truth.
Fairness requires a caveat that most treatments skip: not every either/or is a fallacy. Genuine dilemmas exist. A whole number is odd or even; a switch is on or off; sometimes circumstances really do narrow options to two, and pretending otherwise is its own kind of evasion. The fallacy lies specifically in asserting a binary where the alternatives are not in fact exhaustive — so the question to ask is never "is this a binary?" but "are these two options really all there is?"
The response is to refuse the choice and name what was left out. If told you must choose between security and privacy, the useful move is not picking one but asking which specific measure, delivering how much security, at what specific privacy cost — a question the binary was constructed to prevent. Philosophy is full of examples of exactly this move: much of the free-will debate is compatibilists insisting that "either we are determined or we are free" was a false dilemma all along.