It is very clear in the Bible that Jesus was a Jew. He reads the Torah in the temple. He is called "King of the Jews" by many. At his crucifixion, the Romans even put a sign on his cross saying "King of the Jews." (I would assume that by saying "King of the Jews" one would imply that he is a Jew.)

It is mind-boggling to me that anyone would suggest otherwise. Silly me always assumed that everyone already knew that Jesus was a Jew.