Why doesn't the fellow who says "I'm no speechmaker" let it go at that instead of giving a demonstration?

Why doesn't the fellow who says "I'm no speechmaker" let it go at that instead of giving a demonstration?

为什么那个说“我不是演讲家”的人不就此罢休，而不去做一个演示呢?

-- Kin Hubbard 金·哈伯德