Why do heroes often do something stupid? We rail against a too stupid to live character, screaming, at least in our heads, 'Don't go in the basement!' But when a hero's actions are perceived as stupid, we cheer them on.
Ben Hur for instance. Before the chariot race begins, he removes his helmet. He's raced before. He should know what might happen if he falls from his chariot. Or someone tries to smash his head with a whip. But no, our hero will prevail. . .bare headed.
Or Luke Skywalker. Just when the action gets intense--he turns of his targeting computer. We know the Force is with him, but those he's trying to protect and save really don't have a clue. Is someone muttering a 'long time ago in a galaxy far far away' sentiment equal to don't go in the basement? Because without a targeting computer, he's toast. Or, maybe not. :)
And, have you noticed the villain often has some sort of cheating going on that directly affects the hero's heroic stupidity? Like Masala's chariot wheels--with sharp, pointy things designed to destroy the competition.
But, that's all part of what makes a tale interesting, isn't it?
What examples in movies or books have you seen where the hero does something heroically stupid?