Refusing to answer a question directly is not deceitful. Posing a question in response to a question leads one to think for himself.
Whether it is sinful to lie in all circumstances is subject to debate, and has been taken up by the likes of Aquinas, who famously wrestled with the question.
Is it a sin to lie to someone who is searching for your children because they want to do unspeakable harm to them? To say you don't know where they are when you do? What if saying "I'm not going to tell you" actually endangers them more than a lie?
I'm not saying I have answers. I just don't think it's that cut and dry.