The issue is not technocrats vs moralists. The issue is consequentialist morality vs non-consequentialist morality. In economics, bygones are forever bygones. But bygones are not always bygones in the economy we study.
"The fact is that labour once spent has no influence upon the future value of an article: it is gone and lost forever. In commerce bygones are forever bygones; and we are standing clear at each moment, judging the value of things with a view to future utility."
The famous phrase "bygones are forever bygones" was part of an attack on the labour theory of value, and by extension on all cost of production theories of value. However much labour or other resources were needed to produce an article in the past is not what gives it value. It is the future (marginal) utility that determines its value. But Jevon's phrase also reflects how economists view the world in general.
(Until writing this post, and checking what Jevons had actually said, I always thought he had said "In economics bygones are forever bygones".)
We assume that people are forward-looking consequentialists, choosing whichever action at each point in time will give them the greatest benefits from that point forward, and continuously re-evaluating their choice from scratch at every future point. We ourselves, when making policy recommendations, are usually consequentialists too. We recommend whichever policy will give the greatest benefits from this point forward. Economists are consequentialists in both positive and normative analysis.
But the economy we study is not consequentialist. People are not (always) consequentialists.
We study contracts, like debt. I owe $100, and repay that $100, because I borrowed that $100 in the past. I don't give $100 to the creditor because I think he could make better future use of $100 than I could. I certainly wouldn't give him $100 if he and I both forgot that I had borrowed from him in the past.
We study property rights, and the exchange of property rights. I own my house because I bought it in the past. I certainly wouldn't go back there this evening if I and everyone else forgot that I had bought it in the past.
The very economy we study could not exist if bygones really were forever bygones.
Do we choose whichever policy is best from this point forward? Does it matter whether that policy would benefit those who got us into this mess in the past?