The problem with social justice theories is when implemented result in their exact opposite. The death toll of communist's regimes in the 20th century go above 100 million..[just counting the USSR and China. That ought to put some kind of damper on the enthusiasm these theories. The proof is in the pudding.  And no matter how well thought out a theory is, if it predicts results [prosperity and peace for all] -that turn out to be contrary to its predictions--that theory is false.

But this applies to religious delusions also. The allure of the religious world is their claim of peace and justice for all which is the opposite of the truth. 

The further one gets into areas of numinous content [powerful spiritual presence] like music, art, justice, spiritual values, the less concepts of pure reason are applicable. See Kant (and the Kant-Friesian School). The issue is this there is analytic knowledge which is true by definitions; and synthetic knowledge e.g. there is a continent between Asia and Europe.. There is also a priori knowledge (known, but not by the senses) and a posteriori knowledge known by observation . So can a priori synthetic knowledge  exist? Kant shows how, but only within a certain limit. That limit is "the conditions of possible experience".So when people try to show by pure reason principles things are can not be observed by the five senses and not within the area of possible experience, then you know they are getting into an area where reason not only is invalid,  but is also destructive.]