Independent presidential candidate Ralph Nader campaigned on college campuses in Omaha and Des Moines this past week, and the consumer rights crusader sounded a familiar theme: it’s time for a crackdown on big business. Nader says the drive of giant agribusiness corporations like A-D-M, Cargill and Tyson Food is destroying the family farmer. Nader says Congress should pass legislation and federal antitrust lawyers should file lawsuits to break up their monopolies. Nader says those corporations are displacing many farmers and ranchers, and reducing others to mere peons as the companies force farmers to sign contracts to raise crops and livestock. Nader says monopolies should be a major issue the presidential campaign. Nader says a group he helped start to combat the problem has a website — www.competitivemarkets.com — that has more details.Nader says big business is depleting and exploiting rural America, and will soon displace most farmers. Nader first gained national attention with a book titled “Unsafe at Any Speed” that criticized the auto industry for its safety record.