In 2017 a person I did not know emailed me to call me a kapo—a concentration camp prisoner who agreed to work for the Nazis. What had I done to deserve this? I had signed a letter that criticized then-President Trump’s decision to recognize Jerusalem as the capital of Israel. I suspected that the letter would provoke debate and discussion, as anything that touches the topic of Israel and Palestine tends to do. I did not expect to be called a kapo. Of course, the comparison was extreme—how is thinking that Jerusalem should be shared between Israel and Palestine akin...