Introducing Avada Kedavra

Here is another thing that struck me in viewing the trailer for movie 4, and one of the reasons I still ride the fence on the Snape question and still have strong reservations about the use of Avada Kedavra. It seems to me quite possible that, when we the audience are introduced to the 3 unforgivable curses, Rowling gives a "tip-off" to something being wrong with Moody in the fact that "he" (the Barty Jr fake Moody) would even use the unforgivables at all, even on something as inconsequential as a spider, without real need . I know the arguments for Snape actually using it and still being good posit some form of real need, I'm just trying to make the point that it seems for her any use of it is cause for doubt, any material involvement with instigation or performance of the curse (as opposed to the simple removal of a protective magic once the effects were inevitable, and the removal inevitable as well ... at that point Dumbledore and Snape may very well have cause to choose the time and manner in which the stopper was removed and the "perception" those factors might help them with). Keep in mind that this is a point precisely on which Dumbledore disagreed with Durmstrang's philosophy. At Hogwarts they teach only defense against the dark arts, but Durmstrang teaches the dark art themselves ... but under the pretense of saying that this makes for a better ability to defend against them. Just a few thoughts to ponder ... now it is off to the land of triangles and pies. I have found it best to do this at a coffee shop, where my computer is not present ... to avoid the temptation to sit and endlessly type my thoughts and ponderings on all of ours favorite underage wizard.