The Jews Slay Haman's Sons

Today I read Esther 9 where the Jews rise up against their enemies and have a day of celebration.  Part of the problem I have with this chapter is that the Jews kill Haman's sons, for the simple reason that they are his sons.  There may be more to it, but we are not told.  I really don't like how in the Old Testament people seemed to have this gangster mentality that if you did something wrong, not only will you be killed, but your whole family will die also.  Perhaps that is where gangsters got the idea from?  I don't know but to me it is barbaric that because their father tried to kill the Jews, and was slain for it, Haman's sons are killed.  Perhaps they were in on the plot and were co-conspirators, I really don't know, but the way the chapter is written, it makes it sound like they found his sons, and just killed them for the simple crime of being his sons.  I have a real problem with that and with the idea that God would punish the son for the sins of the father.  So either the Jews were in the wrong, or there is more to it.  Until tomorrow.