Everyone is welcome to criticize another's opinion, viewpoint, and findings.
When poster one attempts to demonstrate why he thinks poster two's position is wrong, that's not necessarily a personal attack. Occasional remarks like "you're a moron if you think..." do get included from time to time, but the discussion generally stays on a) the initial question, observation, or assertion; and b) the counterpoints.
Sometimes it is easy to confuse criticism or our opinions with criticism of our persons, and not everyone draws the line at the same place.
For example, Scowls and Tugela have their posts attacked repeatedly. I believe that this is because some people find their observations - not the individuals themselves - to be of little or no value, or worse, generally misleading or easily misunderstood.
I have received similar treatment for posting an ideal few ticks from the middle of a fight. My idea is that during ramp-up I'm also slowing, and during wind-down I'm also healing, but in the middle of the fight I'm all out on DoTs. While true (at least to me), I have been repeatedly shown that several of the more vocal players feel that this is misleading and misrepresenting, even with the caveat that it is a short duration during the middle of a fight, because many observers will overlook, forget, or intentionally ignore that caveat, and go around saying that Shaman usually do X DPS when, in fact, that was an outstanding few ticks. Never have I taken these criticisms as an attack on my person.