Actual karma (as in the religous concept of eastern faith and mythology) does not play out until the person is dead though. When it will (acording to the belief) affect what or whom the person will be reborn as.

I do still agree that it is mostly a way to cope with an unjust world though, but a belief that should do more good than bad, however i can also see how it might encourage inaction towards bad actors; and ofcourse what constitutes a bad action is dependent on other morals that might be considered contridictory by others.