...but remember that doesn't mean the Buddha often said to anyone, 'You are a fool,' let alone, 'How on earth did you come to such a stupid conclusion? You must have been born with half a brain and then forgotten to use it!' or anything remotely like it. That kind of speech is not Right Speech by any measure. It is also very poor, unproductive teaching style, and the Buddha's teaching technique (quite apart from the content of his teaching) was brilliant. (As a teacher myself, I tend to notice tricks of the trade. I bow to his skill.
Without even clicking on Cooran's link, I'm willing to bet that you will find teachings like, 'The man who does X is a fool, but you wouldn't do that yourself, would you?' or, 'This is what happens to the fool in his next life.' That is, the 'fool' is someone else, and usually someone not even present, not the student.
Getting back to the OP:
I also have been saddened and/or irritated by the rudeness of some people here. Daily life is an opportunity to practice Right Speech, as we should know. DW should be an opportunity to enjoy it and see its benefits as well as practice it.