From time to time one comes across an extreme version of the "nice but incompetent" character. Not only are they nice and incompetent, they are super optimistic

From time to time one comes across an extreme version of the "nice but incompetent" character. Not only are they nice and incompetent, they are super optimistic, confident and ambitious. They pitch their idea to you. It's a terrible idea that for a billion obvious reasons will fail. What to do? Do you want to be the person to crush somebody's dreams? It's much easier to say to somebody that they made a mistake compared to saying that they simply suck at something and don't have what it takes.