Zachariasz Starzynski
Zachariasz Starzynski voted up Call me Z's answer
If a child asks you a Direct question because they genuinely need help from you because they do not actually know the answer to something, do you think that it's wrong to not give them any kind of response at all (even if the question or situation makes you think that the child is very stupid)?

Yes, its very wrong, to the point of arrogance even. One hopes that inquisitive child will be moved to ask someone else thereafter, as the indifferent adult you describe is unworthy of that child's attention.