Questions of social or individual responsibility become bogged down in "is this too much for me to carry?" What is NOT questioned often enough is, "Why did you want me to carry this in the first place?"
I see this in relationships all the time. An agreement is made (often without really even talking about it, certainly not in these terms) that one person will take responsibility from the other in some way, because it doesn't feel like too much of a burden. And then it grows heavier, and heavier, and heavier. Sooner or later it gets addressed, and the other person (or in other cases, political party, organization, or group) says something that boils down to, "But you agreed to take this on in the first place! It's not different now, so what gives?"
And in a way, they're right. But liberals (really I mean Green, as this isn't about politics as much, but not everyone knows Spiral Dynamics) are often size queens, and this is the lesson they tend to have to learn in order to grow past pluralistic relativism. The size of the burden tends to be far less relevant than the cause of it, or the locus of it.
Too often we agree to take on a burden without really asking about it because we feel like we have enough strength (emotional, financial, whatever kind of surplus it is) to handle it, and only later when we realize it IS a burden do we start to question whether or not we should have taken it on, however small. And when we learn that lesson and begin to ask up-front, all of our still-too-liberal friends treat us like we're being ungenerous because "it's just a little thing," why are you so concerned?
But what doesn't start as a "little thing?" The motivation behind a thing that grows from a little thing into a large thing is so often the same motivation. Why not question it earlier?