act like they KNOW what they are talking about when really it is ALL theory.
The thing is, the ONLY people who state absolutes are the fundy Christians. You will never get anyone else who knows what they are talking about claiming that their theory is 'true'.
But to be a theory, to ascend to that status, requires a falsifiable solution. For example, if someone stated that many ancient people from the same area as the Hebrews also believed that the world was a flat disc and didn't provide any supporting evidence, then their hypothesis would not be a theory.
Part of the problem is that some people do not know what a theory is, they do not know that a theory is the best possible explanation from the evidence we have.
Also, a historian will never claim that his or her theory is true. Unless they are a fundy of course.