I do agree with Stef that by and large, it hasn't made much of a dent just by themselves. However, I do think the argument from effect is still necessary in conjunction with the argument from morality, for the reasons you mention. It's an important part of the whole dialogue, if you have a conversation with someone who can think.
Also, I just wanted to comment, when you wrote this:
There are actually manydifferent schools of economic thought
, with different methods and widely differing conclusions about the effects of different social rules.
The only school who consistently applies the insights from the division of labor and trade, competition and the price mechanism is the Austrian school.
I thought of this quote from Hazlitt:
This book is an analysis of economic fallacies that are at last so prevalent that they have almost become a new orthodoxy. The one thing that has prevented this has been their own self-contradictions, which have scattered those who accept the same premises into a hundred different “schools,” for the simple reason that it is impossible in matters touching practical life to be consistently wrong. But the difference between one new school and another is merely that one group wakes up earlier than another to the absurdities to which its false premises are driving it, and becomes at that moment inconsistent by either unwittingly abandoning its false premises or accepting conclusions from them less disturbing or fantastic than those that logic would demand.