Becareful how you say that. For example, in WWII, on the battlefield itself, the Allies used the same military tactics as the Nazis.
Was that cheating?
Nope.
Those were TACTICS. So you are saying that just because an offensive team (football for example) might run the ball to the left, and then the other team does that same, THAT constitutes dirty play since the other team did it?
Hell no. It's a blatant disregard for the rules. That is generally the accepted definition of "playing dirty". Did you mean something else?