Bill Loud was not the first person to play the role of a father on television. What made him a pioneer was that he was not acting — and that he was often not acting responsibly. In 1973, when PBS broadcast “An American Family,” Mr. Loud, who died on Thursday in Los Angeles at 97, was the tan and philandering head of an affluent real-life household whose domestic dramas in Santa Barbara, Calif., were captured on camera for 300 hours and edited into 12 hourlong episodes now regarded as the genesis of reality television. “An American Family” shocked American families....