It is unfortunately a common human reaction to respond to criticism by attacking those leveling the criticism, rather than addressing the points being made. This is especially true if the criticism is legitimate and one cannot reasonably counter it.
Substantive criticism is also a central part of the scientific endeavor, and so the culture of science has developed a tolerance for harsh criticism and a general understanding that the only proper response is with logic and evidence. Examples of exceptions are legion, human frailty being what it is, but you cannot live in the world of science for long without learning the rules of the game. Peers are expected to pull no punches when criticizing the errors or countering the arguments of their colleagues. Everyone is expected to be their own harshest critic (criticize your own data before someone has a chance to). And when criticized yourself, acknowledge what is legitimate and make appropriate corrections, but feel free to defend yourself against weak criticisms by pointing out additional data, interpretations, or errors in the arguments of your critics.
This meat grinder approach to scientific discourse works. Slowly, bad ideas and claims are beaten down, and only good ideas have the stamina to persist.
But here at science-based medicine we engage not only with the scientific community, but also with the public, and with those on the fringes of science. This means we often engage with those who do not play by the rules of science. A recent example is that of J.B. Handley from Age of Autism. David Gorski and I (and later Mark Crislip) wrote blog entries criticizing their 14 studies website with a detailed analysis. Handley responded with a full frontal personal assault sprinkled with irrelevant accusations. He ignored the vast majority of our actual criticisms, and those few he took on he completely botched.