Yes, I read the edit, but I still think it’s wrong. Liberals don’t fail to take into account the existence of zero-sum economic outcomes when they set policy. They are explicitly responding to the existence of zero-sum economic outcomes when they set policy.
Basically, people on the right say that there are always winners and losers, and we should for the most part just accept that; while people on the left say that there are always winners and losers, and we should do something to minimize the misery which comes from losing.
Similarly, people on the right say anyone can win, and people who don’t win are to some extent to blame for the outcome; while people on the left say that some people are dealt a losing hand from the very start of life, and can’t be blamed for their poverty.
Of the two views, only one of them looks self-serving, and only one of them is self-contradictory. If there are always winners and losers, then not everyone can win, and boot-strapping can’t work for everyone, and we will be left with a bunch of the losers to deal with. So the choice is, we let losers starve, or we figure out a way that they can eat. That’s what it ultimately comes down to.