"allegedly" violating it - he has not been convicted yet, and the presumption of innocence should prevail. We don't know if a jury would find sufficient cause, given the circumstances and the illegal acts that were being covered up, to find sufficient justification.
Kind of like "yes, I went through the red light, but I was carrying someone who had been shot and was bleeding profusely to the hospital as quickly as I could."
There's a problem here which Snowden has also voiced: In a "trial" of this nature justification isn't allowed as a defense. This is talked about in Citizen Four.