Yes, among the many purges Stalin ordered, the purge of the JAC was another one of the terrible things Stalin did. I would say that, considering Stalin was deeply paranoid and had many such groups purged and killed that it's a tall order to say he killed the members of the JAC for racist reasons. Again, he created the JAC in the first place. His reasons for killing the members of the JAC was not "they're Jews and I hate Jews". His reasons for killing the JAC were the same reasons he had for killing many other leaders and groups in the USSR - he believed they were conspiring against him and the communist revolution. I know it's easy to cherry pick facts and then make a story about them, Stalin did not actually single out Jews for purging. They were just one of the many political factions that Stalin attacked. He was legitimately insane by the end of his life and he did horrible things. But none of that actually supports your original goal posts that the communist party of the USSR was a racist power structure that executed pogroms. Again, all the evidence points to the party working against the historical racism that were in the people and power structures and correcting course when inevitably there were failures.