Taking CDing out of it, you still can't say all withhodling of information is deceit and therefore bad. I worked with a special needs little girl (kindergarden) with a genetic disease that she would absolutely die from before she reached the third grade and noone ever told her she was going to die young, it would have been cruel to do so.
In the real world with all it's complicating variables and factors, each unique to the individual circumstance, it is logially impossible for the policy of truth to always be the best policy.