I don't think so. You don't see moderates behaving that way towards moderates. And most of the commenters (though not all) are well aware that BIll O'Reilly is a conservative. Most of the comments don't say something like, "Bill O'Reilly was correct about his claims about Edwin Stanton". They say "You disagree with Bill O'Reilly; this must be because you are a liberal; I am not even going to consider your claims."

The subject matter here was history about Lincoln, and the facts in contention were not political, but questions such as, When was the Oval Office built? What kind of gun did Booth use? Was there a hole in the wall or in the door? So people are not defending O'Reilly's book because they have a bias that makes them agree with him about the content of the book. (I think I'll add that to the post.)