Pushing your opponent out is not dirty at all. No matter what shot it is. Taking steps straight instead of forward makes it difficult for your opponent to get in position to catch the ball. Giving you the advantage. At least that's what I was taught. Arregui is the MASTER at it. Watch him closely next time he throws a cortada or picada, middle court. I would tell the player, "hey don't the ball out in the middle of the court for me next time" lol.