The problem with this question, and it's actually a good question, is that it isolates particular events such as the Holocaust, addressing them as if they suddenly sprung up out of nowhere, an also lumps all the victims together as having something more in common than the fact that they were victims.
If you were to ask, 'are shoe salesmen currently responsible for any bad things that are happening to them' we do not assume that there is any connection between a shoe salesman in Iowa who gets robbed and one in New York who gets beat up, because we are not looking at them as a specific target group. Of course, the victims of Nazis were singled out because they were Jews, or Gypsies or Gay or Communists or disabled. But it was the nazis who targeted them and saw them all as a single group of people. It wasn't because all jews are the same, because all jews are not the same.
So, you cannot really separate historically huge events from ordinary events and then use that as a basis for understanding karma. If you begin with conceptual grouping together, then you might say, "yes, it was their fault because they weren't non-jewish" but of course, that makes no sense.
So, is anyone responsible for the suffering they endure?
Sometimes yes and sometimes no.
If I jump in front of a moving bus, then I am directly responsible for getting hit by that bus.
If I choose to walk on Main Street rather than Broad Street, and I am struck by the Main Street Bus, then I am somewhat responsible for what has happened, because I made a conscious choice which allowed for the conditions to be such that the Main Street bus could (possibly) hit me.
If I am walking down Broad Street, and someone who has stolen the Main Street bus goes on a wild driving rampage down Broad Street, running over many people including me, then I am responsible only in so far as I chose to leave the house that day, again, entering into the realm of possibility that a bus could hit me.
So, the degree to which we are responsible varies.
But if we assume that are always responsible for causing our own suffering, merely because we did not prevent it, then by the same token we would also have to take responsibility for causing the suffering of others as well, because we did not prevent it.
karma is not a cosmic judicial system. It isn't about payback. that is a common misconception.
But speaking of the realm of possibility, can one be reborn there? Possibly?
Profile Picture: "The Foaming Monk"
The Chinese characters are Fo (buddha) and Ming (bright). The image is of a student of Buddhism, who, imagining himself to be a monk, and not understanding the true meaning of the words takes the sound of the words literally. Likewise, People on web forums sometime seem to be foaming at the mouth. Original painting by P.Volker /used by permission.