Jay Nordlinger nails one of the big problems with historians, or at least some of them, over at NRO: [full disclosure: I will be history grad student as of this fall]
A classmate of mine asked a distinguished historian, “Barbara Tuchman: Is she a historian?” The professor reflected for a moment. Then he said, “She’s a writer.” Some of the students snickered. At that moment, I figured Tuchman must be worthwhile. Which she is.
It's true that some historians can be perhaps a little snooty about the uninitiated treading on their turf and exceeding them in recognition. It's certainly no accident that some of the most-recognized and greatest American historians- Barbara Tuchman, David McCullough, and Shelby Foote come to mind- have been writers by trade rather than credentialed historians. The best academic historian I've ever read is probably James McPherson, whose Battle Cry of Freedom is both historically sound and very readable, as is his lesser-known For Cause and Comrades. Readability and writing quality have a lot to do with how successful historical writing is.
As with any class of academics, however, historians are rather easy to pick on. History is a bit like political punditry in that anybody with a basic understanding of sentence construction can pretend excellence at it. It is also true of history that doing it badly is quite easy, and I think this is part of the reason historians can come across as a bit snobbish with regards to "non-historians" intruding on their bailiwick.
There have no doubt been great historians who are not "professionals." There are also, however, lousy historians who are not "professionals." Take Joy Masoff, the author of the grade school textbook Our Virginia: Past and Present, for example. Masoff landed herself in hot water in October 2010 for writing a sentence including the words "Thousands of Southern blacks fought in the Confederate ranks," a phenomenon not thought to be widespread by most historians who have studied the subject.
So where did this claim come from? Internet research, and her apology was just delightful:
"It's just one sentence. I don't want to ruffle any feathers, If the historians had contacted me and asked me to take it out, I would have."
Basically, she couldn't be bothered to do much in the way of rigorous research on the topic.
Do historians need to get off their high horses periodically and remember that even those who don't sit at the cool kids table often have intelligent things to say? Absolutely. They are also, however, justifiably leery of those who tout themselves as serious history writers, yet don't really know what they are talking about. Some of the best history out there is by "non-historians," but many non-historians are more than capable of producing utter tripe.