A central Leftist belief is that it is not just to simply leave another person alone, but rather that justice in some circumstances requires a person to actively help another.
That is not an unreasonable principle. For a concentration of people to live in proximity, it is necessary for some forms of positive right to be respected.
But they do insist on taking it to the absurd.
Greeks cannot get money from the banks, because the banks are closed. The banks are closed because they do not have any money. They do not have any money because the ECB (“The Germans”, if you like), have stopped giving them any. The left are describing this situation—Germany not giving Greek banks any more money—as an attack on Greece. By not giving Greece money, Germany is overruling Greek democracy. It is imposing austerity.
You can make a case that if the wealthy of Britain, say, are not paying taxes to fund various generous services and subsidies to the poor of Britain, they are in some way depriving their neighbours and countrymen of something they are entitled to. To be a property-owner within a stable society, arguably, implies duties to that society. It’s hard to see where to draw the line, but it’s not outrageous.
But to posit in the same way, that the people of Germany have the moral duty to fund the people of Greece to live a first-world lifestyle in a third-world economy, is just baseless. They are not fellow-countrymen. They are not neighbours. They do not share a common inheritance from a community of ancestors. Even descending into the swamps of democratic theory, German taxpayers do not get to vote for the Greek government. It’s just blatantly insane. There is no starting point for an argument to begin to work towards that conclusion.
By making or supporting that claim, leftists are undermining their more supportable claims for egalitarian policies within societies. If they can argue for Germans to subsidise Greeks, then there is no conceivable limit to the level of charity they will consider a moral necessity. Therefore whatever level they do argue for must be opposed; since they clearly cannot themselves limit their demands, their demands must be limited for them.