Charity always challenges structures of oppression, because charity refuses to "other" anyone. Charity always challenges social relationships because it refuses to conflate individual people with the systems that shape and deform their behavior towards others.
Charity is understanding. While it sees things as they are, it refuses to accept that people cannot break free of the systems they inhabit. It exercises generosity of spirit and refuses violence even toward the oppressor which is, of course, what Christ commanded when he said "Resist not evil."
Let us not conflate the virtue OF charity with the act of giving TO charity. Both of which are noble but aren't nearly the same thing. Charity isn't measured in whether giving is modest or abundant. That's the wrong notion. Acts of giving while called "charity" are a far cry from the virtue -- which is about extending humanity to others regardless of whether they are those oppressed or those oppressing. Those culturally acceptable or unacceptable.
The act of giving is good only to the extent that it is a symbolic representation, but not a replacement for, the virtue -- which requires not OTHERING other human beings, but meeting them where they are in a poisoned system and letting love heal what is broken.
The problem with our understanding of charity is that we see it as transactional rather than relational. Just like the sacrificial system in ancient Israel, we seek substitution to pay for the sin of our lives -- the brokenness of relationship with self, God, and other. What the Kingdom does is refuse this. Instead, God offers God's own self. As a model. In relationship to us, and particularly to the broken. Not substitution, but self offering and engagement in love and forgiveness and mercy. In charity! This is why we say Jesus is part of the Godhead.
Charity is the act of giving oneself, rather than substituting pigeons, or lambs, or a check to the local NGO. The virtue of charity is self-offering. Not the offering of something else in our place in order to avoid relationship which requires us to engage with the other we would marginalize. Or even the other who oppresses within the broken and damaged systems of this world. Those who exercise true charity make no peace with oppression, but neither do they withhold authentic engagement or relationship with the oppressor.
When you enter relationships characterized by self-giving love, it then becomes imperative that those you "see" cannot be allowed to hunger, thirst, languish, or be denied freedom and dignity. It also becomes imperative that they not be allowed to remain blind to their participation in the mechanisms and systems that destroy human dignity. That they are also bound in chains. That the assault to any is an assault to all that merely hasn't claimed the "victor" yet. Charity insists that all are redeemable. All are worthy. All are broken, but not so broken as to be beyond love. Only the Devil believes that. In other words, it is contrary to the Gospel to divide what God seeks to make whole.