In Burt Reynolds' biography, he said....
When it came time to shoot the rape scene, Reynolds said Ned Beatty really wasn't that keen on doing it. Would anyone be?
He said John Boorman knew he'd only get one chance to get the take, so Boorman privately told Bill McKinney to give it everything he had and to go as far over the top as he could. McKinney followed his instructions and gave it 120%.
Reynolds said they were completely floored by McKinney going so far, and he said they demanded that Boorman stop shooting. According to Reynolds, Boorman kept shooting.
Reynolds said that when the scene ended, Beatty was so furious he jumped up and proceeded to beat the living hell outta McKinney. Reynolds ended the anecdote by saying no one stepped in to stop Beatty from pounding on McKinney...in fact he said they all enjoyed it.