Plus it is possible for people to learn, grow and change. Even know-it-alls.
One thing that I've learned is that no one has all of life's answers. We're all wrong sometimes (though Liberals are definitely "more equal" than the average person in that regard), but that is merely part of being human. Ignorance, which is a lack of information or experience, is no crime. Being unwilling to learn is, IMHO, about the worst thing a person can do.
IMHO, O'Reilly was merely ignorant regarding guns and gun laws before Katrina. Now he is less ignorant, and has recognized that he was at least partially wrong before. That does a lot to dispell my previous distaste for him, because I used to view him as just another self-important guy who ran off at the mouth. Don't get me wrong, he still does that a lot, which turns me off, but at least he's shown a capacity to learn. Now is the time for someone who's really pro-gun that knows him to take him shooting, to show him that semi-autos aren't machine guns, to show him the law that makes bazookas just slightly more difficult to get than a shotgun, etc. I just don't get people who condemn those who have admitted that they were wrong, and who are now moving in the right direction.