How could this saying be reworded for better clarity?

Donald Foster wrote, “No one who cannot rejoice in the discovery of his own mistakes deserves to be called a scholar.” Do you agree? If so, perhaps we could help develop a bit clearer sentence structure for the thought. After all, Foster was just a Professor of English at Vassar. He may not have been the greatest scholar of English syntax.

The way the two negatives are handled in the quote seems clumsy to me. How would you help Prof. Foster reword the quote to better capture his meaning? Or is the meaning not apparent to you?