I didn't know who O'Reilly was, other than some news pundit I didn't watch, until very recently when I began listening to the audiobook Killing Lincoln, which is purportedly a non-fiction work that he co-authored. His reading was so bad I gave up after the first disc. Not only did he read it in a melodramatic way that made it seem like a work of fiction, which made me dubious about the veracity of the content, but when he came to the cavalry battles he said Calvary every time instead of cavalry. That destroyed any credibility he still had remaining in my book. (P.S. I'm an independent, generally conservative). It's no big deal for someone to mispronounce a word, but this was not just a mispronunciation. He continually used the wrong word throughout, probably scores of times. It became obvious he didn't know the difference between the two. For someone who has degrees from two Christian colleges (Marist and B.U.) and taught at a religious school and still doesn't know what Calvary means is shameful, and anyone who purports to be expert enough in a topic (i.e. the Civil War era in this case) to write a major non-fiction work on it, this kind of error serves only to prove the person doesn't know what he is talking about and simply is not credible on any topic.
