A fanatic is one who sticks to his guns whether they're loaded or not.

Jones’s quip defines “fanatic” through a comic literalization of the idiom “stick to your guns.” The joke turns on the idea that steadfastness can become mindless: the fanatic clings to a position (the guns) regardless of whether it is actually effective, justified, or even real (loaded). The line satirizes rigidity and ideological overcommitment, suggesting that true fanaticism is not courage or principle but an inability to revise beliefs in light of evidence. Its punchy structure makes it apt for political and religious contexts, but it also applies to any stubborn adherence to a plan after its assumptions have failed.