Personally I think a more interesting question would be whether you would stop someone like hitler from being tortured to death because even if you assume that there was a historical Jesus that, through his death, would serve as the martyr upon which a religion would grow, there are still a ton of assumptions that have to be made about what he actually said and how he actually went about gaining followers and without more conclusive information in this regard I think it's almost a no brainier that you should stop his torturing and death.
At the time Jesus would have been killed he hadn't been responsible for the blatant and unjust victimization of hundreds of thousands of people, at most you might be able to lay a few hundred on him if he did actually express some of the more controversial ideas of the NT. He probably would have been a small timer even by today's standards if he lived in the 20th/21st century.
Way more interesting of a hypothetical would be whether you would save the life of a person you find absolutely morally reprehensible. Maybe you do think Jesus would have been just as morally reprehensible as hitler though, I don't know.
At the time Jesus would have been killed he hadn't been responsible for the blatant and unjust victimization of hundreds of thousands of people, at most you might be able to lay a few hundred on him if he did actually express some of the more controversial ideas of the NT. He probably would have been a small timer even by today's standards if he lived in the 20th/21st century.
Way more interesting of a hypothetical would be whether you would save the life of a person you find absolutely morally reprehensible. Maybe you do think Jesus would have been just as morally reprehensible as hitler though, I don't know.

Teenaged X-Files obsession + Bermuda Triangle episode + Self-led school research project = Atheist.