Karp is a trash human. His actions have made the entire world less safe and, quite frankly, it's only a matter of time before the Consequence Man cometh for him.
The holocaust was awful, his family did nothing to deserve the persecution they faced. It's GOOD that they were able to thrive in their adopted home.
See? It's actually much easier to hate someone for who they are as a person, than for who you think they represent.