Pretend to be friendly until the interview's over.
Never burn your bridges. Even rude asshole bridges. You don't know if maybe that guy just got a call that his kid has cancer after working an 80 hour week. You don't know if maybe that guy will be hired at your next job. You don't know if he might bad-mouth you to other employers for fun. And you don't know if maybe they're waiting for one more reason to fire his ass. There is no benefit to walking out early, so just wait it out, and then politely inform them you don't think the position is a good fit for you.
Never burn your bridges. Even rude asshole bridges. You don't know if maybe that guy just got a call that his kid has cancer after working an 80 hour week. You don't know if maybe that guy will be hired at your next job. You don't know if he might bad-mouth you to other employers for fun. And you don't know if maybe they're waiting for one more reason to fire his ass. There is no benefit to walking out early, so just wait it out, and then politely inform them you don't think the position is a good fit for you.