“I reject capitalism because people can benefit themselves by doing injustice within it”
No, we oppose capitalism because it inherently ENCOURAGES people to benefit themselves by doing injustice. That’s a crucial difference.
In every system of the world, people can benefit themselves by doing injustice within that system.
It’s equally true that people can be violently bigoted against religious, racial and sexual minorities in every system, but only a few actively ENCOURAGE them to.