State Farm Insurance Co., California's biggest auto insurer, intends to cut drivers' rates by 5.4%, an action that will pressure competitors to continue a downward price trend. The news Thursday means $133.8 million in premium savings for State Farm customers in California.It provoked an angry dispute, though, between Consumers Union, the publisher of Consumer Reports, and state Insurance Commissioner Chuck Quackenbush over whether regulators should be investigating excess profits at insurers and ordering even greater premium reductions.Huge sums are at stake in a state where driving is a necessity for most people. Of California's 20...