Bart Ehrman Writes About Atheist Critics of His Book "Did Jesus Exist?"

I should say that one of the things that struck me, quite forcefully, in the aftermath of the publication of the book, was just how virulent, mean-spirited, and militant some atheists can be. The hate-mail and hate-response that I received for this book from the far left was absolutely as vehement as the hate-mail and hate-response that I have received for other books from the far right. It’s not easy being a historian, wanting simply to know what happened in the past, when so many have so many vested interests in having things their own way. Many of the mythicists are simply fundamentalists of a different stripe. Or so I’ve experienced! LINK.
What I don't understand at all is this phenomenon. Why do atheists get so worked up about the question of the existence of Jesus? Isn't it merely a historical question to be settled in a reasonable dispassionate manner? Don't we have other arguments, plenty of them, showing that the Jesus in the gospels did not exist? I've written about this before in my post Did Jesus Exist? An All Out War is Going On. On this question I do not find Christian scholars attacking atheists but rather calmly trying to explain why they think Jesus existed. What's the problem here folks?