The claims of ahistoricity (the lack of historical evidence) of the new testament’s christ are fairly well established. I doubt there are many secular historians who think that there is any contemporary historical evidence of christ. Even the gospels and other religious texts in the cannon date from decades after the alleged time. The historical figures in the text do not match up with actual historical figures, Herod dies years before the birth of the bible's christ as a notable example. The bible is not a historical work, it is a religious one. It was not written as a historical work and interpreting it as such is a misuse of the text. Arguing for the historical nature of christ is an extraordinary claim, and one that is not supported by contemporary accounts, even the single line reference to christ in Josephus work (which may have been added between the second and 4th century since Josephus scholars of the second century were unaware of it) was far from contemporary (dubiously attributed to a text from 93 C.E). Not being mentioned in contemporary historical accounts does not mean the man did not exist, lots of people fall through histories cracks. Just in case any one is offended I will repeat calling him ahistorical does not deny the existence of some guy called Jesus... it just points out that there ain’t any evidence that he was there until way after he supposedly lived, which is not historical evidence. If the topic was the historicity of king Aurthur I would bitch about that too.
The case for a roman plot... well that is another extraordinary claim. I would like to see the evidence he has to support that, I suspect his evidence is weaker than he thinks it is.