I agree that is one of the more common things to debate, probably more common than what he did say. But that's also only true as long as you confine yourself to the Bible as it exists today. When you look into the history, archeological record, and textual criticism though, things get much more complicated as quite a few more groups wrote about what Jesus was purported to teach than the Catholic and Protestant churches would like you to believe.

Robert Price's, "Pre-Nicene New Testament" is a good introduction to just how diverse and radically different early Christianity was. Bart Erhman is another great author who clearly cares more about what's true, than what fits a churches dogma.