One of my best friends growing up is Jewish. We still stay in contact. The older he gets the more he resembles the typical Jewish stereotype to the point where he could easily pass as a character on Seinfeld. But despite this he is extremely sensitive about Jewish stereotypes and is always looking for signs that people are picking on him because he is Jewish. He has gone off on me many times over the years for saying things that I had no idea had any relationship to Jewish culture.
Several years ago I knew someone who was something of a mental case. He decided to convert to Judaism. I was a bit surprised that he found a synagogue that allowed him to convert since he seemed like an obvious nutjob. But after that if anyone objected to his bizarre behavior, they were anti-Semitic in his eyes.