I get called Hacker couple times when i play online shooters. mainly then when im merely reacting faster than the enemy and somehow through sheer dumb luck manage a headshot, or some other crazy feat that seems utterly impossible.
Obviously the problem is not really being called a hacker, the problem is that it comes from those People that cant take anyone ever being better than they are, or just lucky or whatever. A noob, the worst kind, like the lowest scrub possible, with the mindset of "im the best player ever" will NEVER outgrow that "you hack"-calling phase.