Jesus Christ is pretty unquestionably the central figure of Christianity. His name is where the religion comes from, after all, and the story of Christ allowing himself to be killed by the local Roman government as penance for the sins of humanity is integral to the entire ethical system underlying Christian thought.
However, Robert F. Shedinger, a professor at Iowa's Luther College, has a different argument. He thinks Jesus was actually...a Muslim. Yes, really. In fact, he wrote a book explaining all about it:
Shedinger explained his argument this way:
Got that? According to Shedinger, Islam is a "social justice movement," not a religion, and since Christ supposedly supported "social justice," that makes him a Muslim. To quote him, "I came to the conclusion that [Islam] was a social justice movement and I think that’s who Jesus was in the first century so I conclude Jesus is more like a Muslim."
Where do we begin with what's wrong with this picture? The first and most obvious point would have to be that Christ, being born roughly 600 years before Islam even existed, is not capable of being a Muslim. To be sure, if you believe there are commonalities in values between Islam and Christianity (which scholars in both faiths do, in fact, believe), you could argue that Christ held some Islamic ideas. But to claim that he was a Muslim is to take it entirely too far.
Moreover, if we are talking about which religious founder actually got his ideas from the other, would it not be more accurate to say "Muhammad was a Christian." After all, if Christ's teachings are virtually indistinguishable from Muhammad's (which seems to be the main thesis of Shedinger's argument), and Christ came first (which he unquestionably did), then clearly it's Muhammad who ripped off Christ, not the other way around. Of course, a book titled "Was Muhammad a Christian" might get a sizably larger amount of backlash from some of Muhammad's less...shall we say, "socially just" followers, but it also would have been more intellectually honest.
Finally, about that "social justice movement" description, we'd like to hear more of an explanation about how a religion that encourages female circumcision and conquest of any and all unbelievers is somehow tied to "social justice," or, if it doesn't support these things, why people who believe it does are wrong. We also wonder why a social justice movement would be based around a belief that there is no God but theirs and their founder is the only legitimate prophet. We expect to be waiting a long time regarding these points.