There are different types of cedar. I think most of the articles advising against the use of cedar bark in mulch are advising specifically against red cedar (Juniperus virginiana), which can be allelopathic.

As for this statement by Dr. Dirt -- "The best mulch for any site anywhere is recycled plant material (leaves, twigs, spent plants, buds, bark, flowers and other plant debris) that grew on that property. That's the natural way it is done in the forest and on the prairie" -- he's right, of course, but his explanation that this is the natural way it's done in the forest and on the prairie probably means that he's talking about "recycled plant material (leaves, twigs, spent plants, buds, bark, flowers and other plant debris) that grew [naturally] on that property." Gardens are a far cry from forests and prairies. We plant things that compete with one another and can be harmful to one another. Many of my neighbors planted sycamore trees, for instance, and then planted roses and other things around the sycamores. Unless they bag up all of the sycamore leaves and send them to the dump, they find that those leaves are likely to kill their other plants, especially roses. My neighbors who planted eucalyptus trees have the same problem.