That's a famous quote and age might have mellowed him. But he was not like that at all in person with his students. He did insist that one be precise with ones words.

The origin of the quote may have more to do with cultural differences between the Dutch and Americans.

Alan Kay himself said this quote is taken out-of-context and so people need to stop repeating it - https://news.ycombinator.com/item?id=11799963