I believe that certain inequalities that cannot be forbidden in the name of socialist equality of opportunity should nevertheless be forbidden, in the name of community. But is it an injustice to forbid the transactions that generate those inequalities? Do the relevant prohibitions merely define the terms within which justice will operate, or do they sometimes (justifiably?) contradict justice? I do not know the answer to that question.
I continue to find appealing the sentiment of a left-wing song that I learned in my childhood, which begins as follows: "If we should consider each other, a neighbor, a friend, or a brother, it could be a wonderful, wonderful world, it could be a wonderful world."
Market socialism does not fully satisfy socialist standards of distributive justice, but it scores far better by those standards than market capitalism does, and is therefore an eminently worthwhile project, from a socialist point of view.
The natural tendency of the market is to increase the scope of the social relations that it covers, because entrepreneurs see opportunities at the edge to turn what is not yet a commodity into one. Left to itself, the capitalist dynamic is self-sustaining, and socialists therefore need the power of organized politics to oppose it: their capitalist opponents, who go with the grain of the system, need that power less (which is not to say that they lack it!).
Every market, even a socialist market, is a system of predation. Our attempt to get beyond predation has thus far failed. I do not think the right conclusion is to give up.