Feeding hungry people seems to us so obviously a good thing that we do not even take much time to justify it. It's something we all know. If the hungry live in other countries or are otherwise perceived to not be "ours" we might regard it as of little concern to us, or not our problem, but we don't condemn others who want to go fix it. We regard them as kindly and noble. Unrealistically kindly and noble, perhaps, but not evil.
In the practical world this is not as clear and clean as we'd like - for example, if we put the other nation's farmers out of business by destroying their market we may have created a worse situation. But ignore that for the moment, and pretend that giving food is an unmitigated good, if only in theory.
Freeing politically oppressed people we regard as more ambiguous. We are far more likely to treat such situations as none of our business and not our problem. Further, we look at people who want to intervene in these situations as more suspect. The obvious reason is that to increase freedom for some group of people, we have to do something against some other group. We might have to tax them, shame them, arrest them, or kill them, but there are others in the equation now. To do something for one group necessitates doing something against another.
Is that really a large difference? Our emotions tell us it is. Feeding = good; killing = bad. Non-western cultures make this distinction far more weakly or not at all. Even in the west the distinction was not so strong even a century ago. This impression of a great moral superiority of the one type of rescue over the other is not new, but its commonness is new. When values change, it is interesting to ask why.
I think resistance to judging others enters into this change. To be nonjudgmental is currently one of the highest of virtues in western cultures. To intervene for one group against another implies a judgment. It is now fashionable to declare we have no right to judge.
How do you think this looks to a person who knows without doubt that they are being oppressed by evil and corrupt rulers? To a person who knows as clearly he is oppressed as he would know he was hungry if he had no food? How would our distinction about not judging look to that person?
I think he would regard us as merely cowardly or uncaring, not morally sophisticated.