They also do it cause they find it funny. I men look it has happened to just about everybody once. Someone cheats, you lose, get pissed, quit playing, and then decide to show your maturity about it to complain about it online validating their actions in the process.
You enable them by getting angry!
In other words, go back online, play against the cheaters. Take it like a man or woman depending on gender. Wait for them to get bored because you keep playing and do not care. They will get banned eventually so stop crying because you make it worse.
Showing an ounce of weakness to someone who drives you nuts keeps them doing it. So, relax and just watch them get banned or watch them get bored because you do not care. And of course remember most of all to stay zen minded!!!
Anger clouds your judgment causing you to react without thinking. Stay calm and don't give them the satisfaction and don't sink to their level either! Your better than that ! Good luck and good gaming to you.