It seems to me if there is the appearance of the Obamas using their children as billboards for their own political beliefs, then criticism of the Obamas is perfectly appropriate.
The article clearly stated that SHE chose to wear that shirt, it was not chosen by mom or dad. Unlike the younger daughter, photographed with a peace-sign tee as she's coming down the plane steps with 0bama later on in the thread, now that one I figured was handed to her by one of the adults. But the article in question was unambiguous.