The vandalism that happens around meetings like the G20 is usually said to target multinational companies. That way, it's supposed to deliver some sort of a message that's not just about people being able to break things.
Pizza Pizza is a Canadian company, and is almost entirely composed of locally-owned franchises. And as if that's not enough to put it on the good-guy list, their cheap-and-decent food makes them a long-standing staple for students. Whoever broke the windows on this one was just being a complete f`king idiot.
(This post concludes my G20 series, partly because finding appropriate song titles has become a bit of a stretch.)