1. OK, I agree that pointing fingers about this is completely pointless. Accidents happen. This was unlikely to have been the fault of any specific group of people, save perhaps the deceased pilot(s) and what's the point in that? It seems that this sort of thing was bound to occur given the congestion in that airspace.
2. But WTF are you talking about, a day to mourn? Mourn who? Mourn what? Did you have friends or family on the plane? If not, wtf are you talking about? Nobody is stopping you from "mourning" whatever that means to you. Do you mourn all the people who died of cancer yesterday? Or a heart attack?