Reason is not automatic. Those who deny it cannot be conquered by it. Do not count on them. Leave them alone.

Rand is stressing a central Objectivist premise: reason is a volitional faculty, not an involuntary reflex. People must choose to think, to check evidence, and to follow logic; if they refuse that choice, rational argument has no “hook” to catch on. The line is also practical counsel: don’t waste your life trying to “defeat” irrationality by piling up proofs for someone who rejects the rules of proof. Instead, withdraw your time, attention, and moral sanction from those who evade reality, and reserve engagement for interlocutors willing to use reason.