Not quite sure how Dangerfield made the list. Yea, he was a comedian and he may have been Jewish, but his act was far from clean. Funny as Hell, but he used swear words.
On the other hand, I saw Red Skelton at Circus Maximus in Caesars in the late '80's. The worst thing he said was 'Damn' once and he had the place in stitches all night.