Interesting, I’m surprised that you think the average person feels shame over the actions of bad people. I would have said sadness in sympathy to the victims and disgust for the bad person
Heck, most of us are effectively different people than we were in the past. And we very much feel some shame when we find out something bad we did back when.
Do you feel shame when you read about someone stealing a bike in a far country whose capital you wouldn’t know ? You must be in despair over all the crimes committed by humanity every hour
Do I also think it is arbitrary? Yeah. But I am also ok not feeling shame at stupid crap my immediate family has done. I just have no surprise that others do.