The rural male who sits on his front porch in summer without a shirt is not a good risk, according to the Continental Insurance Home Owners Manual.

On the second day of hearings on discrimination and redlining by automobile and property insurance companies, Sen. Howard M. Metzenhaum (D-Ohio) returned frequently to this vivid example. On what statistical evidence he wondered, had insurance actuaries decided men wearing shirts were better risks. The question went unanswered.

It was industry's turn yesterday to testify. Witnesses from trade associations and the Hartford Insurance Group defended classifications based on age, sex, occupation, geography and subjective categories such as job satisfaction. Anton A. Lubimir, a vice president of the Hartford Group, said this system helps to prevent underwriters or rates based on one factor such as a single accident or violation.

In another example, George A. Mulligan, a vice president of the American Insurance Association, said that, because the theft rate for vehicles at Kennedy Airport is very high, anyone who would park there would be a bad risk, and because most people who park there come from New York City urban rates should be higher.

Metzenbaum retorted, "But what about those people from Westchester County and Connecticut" (where rates are lower)? "I never heard of a manual that rated on the basis of where you park your car, only on where it is garaged."

Carl Levin, former president of Detroit's city council, called property insurance redlining there "pervasive and pernicious" and presented evidence of insurers cancelling or refusing to write policies solely on the basis of location. The location, most frequently, is the inner city or a declining area.

C. Robert Hall, vice president of the National Association of Independent Insurers, described the problems of insuring older dwellers in neighborhoods with abandoned houses and high crime rates. If a house is worth $15,000 but would cost three times as much to replace, no company would be willing to insure it for $45,000 for fear of arson, he said. And if the policy's value is only $15,000, the premiums would not be sufficient to replace the house after damage has occured, Hall added.

For this reason, the association is trying to persuade insurers to write policies based on actual repair costs using modern materials up to the home's market value, instead of the replacement cost. For instance, the $15,000 home that went up in smoke might have contained solid oak floors and stained glass windows. The insurance company would agree in advance with the policy holder to repair the windows with ordinary glass and to lay a pine floor.

Donald J. Jordan, vice president of the American Alliance of Insurers, described what he called "an early warning system" for state insurance commissioners: a company's surpluses are too high when its reserves outweigh premiums by more than 3 to 1.

Unconvinced, Metzenbaum accused the insurance industry of being "nothing but monolithic economic giants. The American people have a right to be concerned."

Metzenbaum's committee is looking into the possibility of repealing the McCarran-Ferguson Act of 1945 that made the insurance industry exemptfrom federal antitrust laws because it is entirely regulated by the various states.