Push-back is fine. Revenge is not.

Push-back is strategic. Revenge is impulsive.

Push-back establishes boundaries and signals the consequences of violating those boundaries. Revenge accomplishes nothing except temporary self-gratification and is actually self-destructive.

Push-back has a chance of sending the intended message. Revenge is likely to send the wrong message and is more costly.

Push-back helps you win the game. Revenge takes you out of the game.