I concur with this assessment. Sload are not "Evil", nor are they "Good." They are "Different" and "Alien." This is why I think the Thrassian Plague was not created out of enmity, but more likely created for political or economic reasons, as I postulated earlier.
The sload strike me as being highly "Mundane Thinkers" (EG, they less inclination to hold the reverences of "Divinity" that EG-- Humans have.) and as such do not have the same kinds of scruples that we have. What TES authors describe as "exagerated" emotions toward loss or incompetence might not really be exagerated, but just misinterpreted emotional outbursts from an alien mindset. Given the behavior of N'Gasta, I would suppose Sload society advocates "Creative" problem solving, the ability to adapt and flourish in adverse circumstances (including intellectual pursuits), and a somewhat unspoken exaltation of freedom from moral entrapment.
What to humans would seem like "An obvious choice to choose the good and righteous path", might seem like silly superstition to a Sload. The sload strike me as the kind that HONESTLY believe that there is simply no such thing as right, nor such a thing as wrong. There is only that which can be shown reliable, true, and useful. This is why I suppose that the "Emotional outbursts" of sload concerning incompetence is in fact a real emotional outburst, and not one put out in the name of grand theater. Incompetence would seem to be highly despised by sload society, as it would be seen as a sign of being fundementally incapable, and therefor worthless. It is not logical to use an ineffectual agent to accomplish ANY task-- and as such, the sload that sent the agent, believing that they WOULD accomplish said task, only to have that agent fail, would reflect poorly on the sload in question themselves-- a very unpleasant thing indeed, and quite worthy of being lamented.
It may also explain the Sload's preference for using reanimated servitors, since the reanimated are less willful, and less likely to stray from their master's commands, and are thus more efficient, and better reflect the capabilities of their master's intellect. It seems logical to me that a powerful, and effective necromancer with good, and efficient renanimations would be highly venerated in Sload society, as it would reflect favorably on their reliability and intellect.
I find it a reasonable assumption that the Sload consider the Thrassian Plague incident to be a "Colossal failure" on the behalf of it's orchestrator-- for failing to contemplate all of the applicable factors into the plan. They wouldnt have found any kind of moral objection to using a plague against another species, (Or even internally, against their own species for that matter.) What they would have found repugnant would have been the fact that the reason it failed, is because of improper planning and calculation (Eg, Incompetence.) As such, because the plan resulted in Thras being shelled out of existence by the allied Tamrielian Navy, I feel the sload would hold the creators and planners of the Thrassian Plague plan in high disdain, and as examples of how NOT to formulate and carry out a plan.
They strike me as being firm adherents to notions like "The only time stealing is wrong is if you get caught" and such associated ideologies. ("If the system lets me do it, then it is not cheating", etc..)
In short, the sload strike me as an entire race of sociopaths, who are actually beyond such a description.
This plays in perfectly well with the Moral Ambiguity of the TES universe, since to THEM, we would appear as a bunch of bleeding heart sympathetic fools who are slaves to romantic notions of pure foolishness, and are incapable of understanding 'true reality.' As a result of being so beholden to such totally inprovable and untestable notions, they would find us to be highly erratic, unreliable, chaotic, and outright inscrutably insane. They might even wonder how it is we even function as societies at all.
The sload show us a side of ourselves that most people are unable (or afraid) to commune with or associate with, because of its alien feel, even though it is indeed an inseparable part of ourselves. They show us our inner sociopath, which is concerned only with our own success, and how we can make use of what and or who is around us for our own comfort and amusemant.