I'm not intimately familiar with AlanF's participation here. But it's contrary to my experience that AlanF would attack things a person said for no reason. On the other hand, if he felt a person's intelligence was anywhere north of idiocy, he would become increasingly aggressive in his presentation of information and responses if the individual refused to learn. For AlanF, that reaction was somewhat of a compliment. It meant he saw intelligence in the person he was engaging. How what he said might make them feel was not something he'd spend much time considering, let alone worrying about.
A weakness AlanF had, in my opinion, was that he tended to discount the extent of influence emotion can have on a person's ability to comprehend. Academically he'd yield that latter point, but in discussion not so much. Some individuals have such an emotional need that there are things they just can't allow themselves to learn of because it would wreck the world they depend on. A person on a ledge we should not push. I'm not suggesting that's the case with the other names you mention. One I've had some decent amount of interaction with and find them pleasant enough and not tide down emotionally. But with AlanF seeing anything through another person's lens of emotion was something he had trained himself to refrain from as a matter of learning, and learning was what he thrived on and lived for.
AlanF and I have both been downrange of one another's conclusions and arguments, so I know that experience. Some of those discussions were more than robust! Thankfully we both gave one another full liberty to speak freely in our exchanges without thought of feelings. But I only know how I experienced it, not how the same would be experienced by another person. Another person could easily find it offensive, or even as an attack. Whether I agreed or disagreed with AlanF (or anyone else!) I always looked for whatever I can learn from each interaction, and there is always something to learn. That said, later in my life I have determined not to spend time suffering fools.