Is using the sociopath label premature or unsubstantiated? Possibly, I know I'm not qualified to assess that, but he does support his reasoning, even if it's wrong. If he had said, "Based on my understanding of what a sociopath is, and the facts as I understand them from Harry Markopolos' book, "No One Would Listen", I think Madoff is a borderline sociopath at least, and possibly an outright sociopath." would you have taken as much offense? Does that sentence not express a useful point of view with respect to the argument that Madoff is different than Holmes?
It's tricky, because our good-intentioned attempts to improve discourse can actually have the effect of stifling discourse when this tendency progresses farther. There are many topics that fall under race and sex that it's hard to rationally discuss because people view the asking of the question itself as insensitive. For example, try posing a question about advantages of a population (race, sex, insular group) based on genetics in a submission here that's related in some way, and you might find you've been down voted and possibly called racist or sexist (likely in more words but to the same effect) prior to anyone actually paying attention to the question you're really trying to ask, and whether it has merit. It's hard for people to stay rational when someone questions the foundations upon which we build a lot of our beliefs (such as people are born equal).
I find a good rule-of-thumb for me in situations where I feel the need to call out the method in which someone raised a point, but not necessarily the point itself, is to pose it as a question and ask whether the method they chose really helped or hindered their point, and to try to do so in a way that's not condescending (which I hope you don't take this comment as, it's surely not intended that way). For example:
"Is the label sociopath really appropriate, and do you think it was needed to make your point?"
In this case, I think scott_s does think it's appropriate (that was made clear), and because of that is was his point. Now, if the original comment was something like "You can't compare Madoff to Holmes, he's in a different category because he's a sociopath." then I would think differently, as there's little useful substance to that comment and it's not really substantiated.
Okay, got that off my chest. Feel free to ignore as you see fit... :)
Thanks for applying the principle of charity! (In case the tone of my text is unclear, that is a genuine sentiment.)