The logical guy sees that everyone can't be saved. There isn't enough food so everyone will starve before more supply can arrive if sacrifices aren't made. The good guys are lost at sea and have to choose between saving the captain (and only one person who can steer the ship) or a child. Whatever, the situation the logical guy will advocate the cold hearted solution that is really the only viable choice that makes sense given what the characters know.
The rest of the good guys will say how it's bad and wrong and suggest something nobler that benefits everyone but is incredibly unlikely to work. Which will then nevertheless work against all reason, thus "proving" that the logical guy should think with his feelings more.