I found several medical studies about dark chocolate by googling in a matter of seconds. Perhaps instead of degrading parents who are trying to relax and ease the stress of child-rearing, you should consider learning to use a popular search engine that even the children of those wine-drinking moms know how to use.
Yes, dark chocolate is great for health in moderation.
The polyphenol/flavonoid content is responsible for many of its antioxidant health benefits. And the magnesium content is also excellent. In fact, significant decreases in blood pressure and overall cardiovascular mortality have been seen in population and case-control studies. It is also associated with longevity (although this is more of a correlation)
However, keep in mind that it is high in calories and oxalates.