My vision of economic morality is more or less Rawlsian: we should try to create the society each of us would want if we didn’t know in advance who we’d be. And I believe that this vision leads, in practice, to something like the kind of society Western democracies have constructed since World War II — societies in which the hard-working, talented and/or lucky can get rich, but in which some of their wealth is taxed away to pay for a social safety net, because you could have been one of those who strikes out.
Such a society doesn’t correspond to any kind of abstract ideal, whether it’s “people should be allowed to keep what they earn” or “from each according to his ability, to each according to his needs”. It’s a very non-Utopian compromise. But it works, and it’s a pretty decent arrangement (more decent in some countries than others.)
That decency is what’s under attack by claims that it’s immoral to deprive society’s winners of any portion of their winnings. It isn’t.