But that analogy is seriously flawed and therefore highly misleading.
Running a red light was always against the law. Going through a red light twice rather than once, or every time versus a few times, is obviously much worse.
But using private email as Secretary of State was not only not against the law, but went against no policy when either Powell or Clinton held that office. Powell did nothing wrong, and Hillary Clinton did nothing wrong. If person A does something that it is not against the law or any policy a few times, a person B does it every time, and that action later becomes against the law or stated policy, neither person has done anything wrong.
It's amazing that Dickerson and all the pundits in the media who are repeating his analysis are so fuzzy on this issue. Our Constitution wisely prohibits ex post facto laws - holding someone accountable for an action which was not illegal when it happened - and Dickerson and his colleagues should know better.