Question

Why do historians need to be worried about reports with a bias in them?

Answer 1

Since they are biased they could be making it seem as if something happened when it really didnt.

Answer 2

Just adding to gdogthegirl's answer, she's right. When you're biased, it means you're showing favor to a particular point of view. History needs to be objective -- taking in every view -- to create an accurate picture. History includes both the good and the bad.

For example, if you're writing a history paper on Disney but don't include things that you think might make Disney look less awesome in YOUR eyes, that's showing bias. Your personal feelings about Disney are creating a bias in how you're writing your paper in that example.