During the 2008 election, B O’Reilly was the king Obama-defender. All those accusations of him being born in Kenya were ridiculous. Having a stolen social security number from Vermont? “Ridiculous, there’s nothing there.” “Oh come on, he’s not an actual communist, that’s ridiculous.” Sure, it’s not like he ever admitted it himself (/sarc). A conservative pulling this kind of 180? It’s not too hard to figure out that O’Reilly was bribed or blackmailed, there’s no other explanation.
Bill is pretty typical of somebody who grew up when and where he did and made it big in media.
An Irish guy from Long Island with a soft spot for the Kennedys isn't likely to be as hard right as some other people can be -- especially if he worked at CBS and ABC on the way up.