You have this idea that you can achieve an absolute.. that you can eliminate corruption entirely. It seems to contradict your idea that it's useless and futile to work toward an impossible/unrealistic goal.
You say:
Do good people advocate “reforming” and “limiting” murder, theft and assault? Or do they advocate ending those things?
Ethical people are happy with either reduction or elimination of these things. Among them, realistic people work toward a the feasible outcome of minimizing evil. If you get hung up on absolutes, then you might as well choose to live in Somalia over Denmark, for example. Denmark has not eliminated corruption entirely, but there's a measurable world of difference between the two (see the corruption index.
Boycotting is something that can have a positive effect on the world. Whenever a boycott catches on and large numbers of consumers decide to participate, it carries weight, using the one power companies understand: money. Recent example: Starbucks.
Hence why I advocate for:
RE: Oppression: Symptoms and Causes