Europeans and others around the world are burning and uprooting test plots of genetically altered plants in protests that they call “decontaminations.” More than two dozen influential British consumer groups last month called for a five-year moratorium on genetically altered crops, while everyone from top chefs to McDonald’s in Britain have promised to eliminate the foods, which are being derided as “mutant crops” and “Frankenfoods.” Americans have been consuming genetically modified crops since 1996 with almost no protest, but two-thirds of European consumers believe the technology threatens human health or the environment.