An executive for electric automaker Tesla Motors used a Michigan seminar Tuesday to take more shots at the traditional auto industry, describing competitive vehicles as “appliances” and bucking the trend by calling for more strident fuel-economy standards. He said he is surprised that there are only lower-performance vehicles in the marketplace and nothing to challenge the Model S. “In some respect, they are appliances, in terms of the way they look.” Tesla, BMW and Nissan electric vehicles are the few exceptions, he said.