I think them motive here is much more damaging to Chris Christie's political ambitions than the actual act is, although you certainly can argue is endangered public safety. But Christie's been branding himself as "a big tent Republican," who can attract a variety of constituencies.
Staff emails that strongly suggest a political enemy was punished at the expense of the public will go a long way toward damaging that brand. And the emails suggest a very childish mentality among Christie's staff. Christie has gone dark, not talking to the media, which suggests he sees this as very, very serious.