Arson is a ghastly crime, of course — menacing, malicious. And it’s good to hear that last night’s burning of the Fox Christmas tree resulted in no harm to any fire fighters or passersby. The 49 year-old arsonist, a Brooklyn resident, was arrested soon after the tree ignited. The initial presumption, of course, was that the tree was torched as a political statement by a Fox hater. There are flammable Christmas decorations all over midtown Manhattan, but the arsonist chose the Fox tree. Do the math.