Being 'brutal' is sometimes ok if the brutality is more like 'exposing reality' in nature, and pointed at a situation, not at individuals.
Personal attacks are totally counterproductive, demeaning, and just mean. When they are public, it's especially way out of bounds and I have no respect for someone who does that, it shows a lack of emotional maturity and confidence.
There are definitely idiots in the world, but you don't go around calling them idiots, and certainly not in public. You don't even call their solutions 'idiotic'. You can say: "This approach is completely wrong, here's why and here are some alternatives" as a fairly callous-yet-acceptable response.
Being unduly cold or callous shows a lack of diplomacy, and as Engineers sometimes we are all guilty of that a little bit, but being specifically derogatory is just bad.
More on topic: congratulations to Guido for his contributions. None of us can never know how hard that was, and how much his contributions have helped so many.
Bravo Zulu.
I wish someone, in some respected 'institution', would give him some kind of medal, or the like.