I know neither enough about Jesus OR R’ Boteach to comment from a place of real undesrstanding, BUT… what I always was taught was that in his day, he never declared himself to be son of any god, nor did he try to start a changed religion. It was Paul who made the big changes that formed early christianity, and all the books of the so-called New T. were written decades after Jesus lived, and even those gospels record the story with changes. they cannot agree on details among themselves. So if they cannot remember something that happened maybe fifty years prior, why would I believe anything that they quote in his name?
I am not saying he was a good Jew, or a Pharisee, or not an Apikorus, or anything, because I really do not know. What I do know is that more destruction to the Jewish people occurred in his name, than for any other reason. He might have been an innocent bystander – according to the Talmud however, he was guilty and chayav misah (from what I have been told, as I never learned this type of stuff). So that being the case, Perhaps people like R’ Boteach should seek to write about something less likely to cause this type of uproar.