By now you've all likely seen the FOX news interview of Reza Aslan by Lauren Green (if not, here's the link: http://www.buzzfeed.com/andrewkaczynski/is-this-the-most-embarrassing-interview-fox-news-has-ever-do?bffb). The general reaction of most has been, "isn't FOX news stupid?". Yes, they are, but it's worth exploring precisely why. It is, of course, possible that Aslan's Zealot is a terrible book. It is also possible that he is biased because he is a Muslim. The key word here is 'because', which has several meanings. The two most important to distinguish are the causal and the epistemic senses. As I've used it above, because is causal (the fact that he is a Muslim caused him to write a badly researched work). The second sense is still causal, however, it causes one to know something (episteme is the Greek word for knowledge). How do I know it is 7am and not 7pm? Because I see the sun in the East rather than the West. Now try that with the Aslan case. How do I know that Zealot is a biased work? Because Aslan is a Muslim. This results in a classic example of an ad hominem fallacy. If you want to discuss bias in Zealot you must first show that it is biased by discussing its content (noting that Aslan does not claim Jesus is god does not represent bias since Jesus' divinity is irrelevant in the field of religious history generally and more specifically in studies of the Historical Jesus). If the work shows bias, then you can ask whether or not the particular biases contained therein represent a specifically Muslim bias).
