Withholding the truth and outright lying are two very different things. They're often grouped together due to their nature of obscuring the truth but lying is a blatant disregard to the truth while withholding information might give away some, but not all of it.
Lying in itself is always a complicated matter. Words have an effect on people, only bolstered by the tone, the emotion, and the people who say it. It gets even worse when people believe the lies spoken. The fallout alone could start riots if not outright wars. Many politicians would use this to excuse their lies.
That it's dangerous, that the truth could put people in danger.
Rarely though are the questions asked so brazen as 'what are the nuclear missile launch codes.' The questions people ask those in power are 'what are you going to do?' People expect change, more often than not for the better. They expect justice and retribution, law and order. These questions aren't always answered and far too often they're met with placation's and lies.
For too long people in power have gotten away with telling lies. Lies they try justify with their greed and desire for power. Out of everyone, the people who should be the most transparent are the ones who affect and control peoples lives. It's not justifiable to lie when you shouldn't lie to begin with.