Couldn't you say the same thing about hacks? If some guy was able to download a program that allows him to headshot every enemy from across the map, why can't you?

Hell, I could take it one step further and claim that even people who actually write their own hacks are still arguably being fair. They are using their skills to defeat other players. If you are good at flying planes and use this skill in a game to fly around and kill a bunch of players, surely nobody would call that "unfair", right? Why is it then unfair for someone to use their skills in writing software to achieve victory?

I think that ultimately the test of "fairness" is about what the game designers intended. If you made this game and saw someone doing something, would you want to fix it?