Shalom Chaim,
I just wanted to say that not ALL of the Cossacks committed violence against the Jews. The Cossacks are actually NOT one single ethnic identity, but a large group of different tribes from all around Russia and Central Asia. The different Cossack groups all have distinct identities, so they cannot be collectively blamed. It is more or less comparable to the differences between the English, the Irish and the Scottish. You cannot really blame the Irish and the Scottish for all of the crimes committed by the English.
Many of the Cossack tribes did massacre Jews, sometimes on the orders of the Czar and sometimes simply of their own accord. But other Cossack tribes did not. The Zaporozhian Cossacks not only respected the Jews, but actually allowed Jews to fight among their ranks. There were a number of Jews in this Cossack regiment, including a colonel named Matviy Borokhovych in the 1600s. The Zaporozhian Cossacks were also notable for fighting tooth and nail against Islam - they were vicious opponents of the Turkish Sultan, Mehmet IV, and they forcibly resisted any and all attempts by the Turks to seize even a tiny part of their territory. I would not have otherwise brought this up, but I think these particular Cossacks deserve to be honored as an example of what modern Russia should aspire to.