Translation: It doesn't fit the liberal agenda.
That sort of museum (and the Museum of the Confederacy in Richmond is a good example) basically gives you "just the facts, ma'am", with lots of artifacts from the period with informative placards on their origin, provenance, etc., biographies of the participants, and a factual description of whatever historical events took place there.
Then YOU do the interpretation, if any is desired.
Of course, this means that you have to be SOMEWHAT prepared when you show up - i.e. have a basic knowledge of the history of whatever you're going to see.
Where modern museums get into trouble is by spoon-feeding "interpretations" to slack-jawed rabble who haven't bothered to learn the first thing about what they came to see. Problem is, "interpretations" are wholly a matter of personal opinion and prejudice, and like certain portions of one's anatomy, everybody's got one. I believe museums should stay the heck out of the personal interpretation business, and leave that for the historians to fight over in their learned journals, where nobody has to pay any attention if they don't care to.