There is so much evil in the world that we as human beings have an obligation to oppose. I have chosen US prisons as the evil against which to crusade. I am not sure why I chose prison reform as an issue; I have never been in jail or prison, and no one I know have either (at least as far as I know). Among the rich and famous, the cause often selected is one they or their loved one experienced personally.
None of us has the time or the resources to actively oppose all the world’s evils. I do not expect to see significant change in America’s prisons during my lifetime, but we must start somewhere, sometime. Some people are already trying to improve our prisons and/or ultimately eliminate them. That is now my goal too.
Some other evils for your consideration to oppose: hunger in the US. Speeding up disaster relief. We Americans are generous in responding to foreign tragedies; we must do more here at home. The easy availability of guns in the US leading to one shooting tragedy after another. Joblessness among minorities. Epidemic of drug use. Exploitation of the poor and the undocumented. Unjust wars-torture. ET CETERA
So take your pick. There are plenty of evils to go around.