I'm sure it has been mentioned in other topics that the kickback you experience when being shot at is only a visual thing. your crosshair is still in the same place. Any attempts to adjust your crosshair as a result will just end up with you missing shots. My guess is that when you shoot first and then suddenly get hit, you try to adjust and counter it. As for the person being shot at first, its most likely that he isn't trying to adjust for any kickback and is reacting, initially at least, based on reflexes, reacting to being shot at and that is why he may be more accurate. Just a thought.