Question: I must disagree with your stand on working against abortion and other widespread American ills. I am commanded in Scripture to "overcome evil with good"....I don't see how I can refuse an opportunity to work against evil just because a Muslim or Catholic may also be doing this work....I agree that we are not to be unequally yoked with unbelievers....But I can't control who might also want to boycott, march, or vote as I do in protest of various evils....I can plant a seed toward their seeing the Light. And if they never respond, I am being obedient in protesting evil and seeking to see that good prevails.
Response: As I stated in the July 2006 Q&A, abortion is evil and should be opposed in preaching, writing, and speaking by Christians.
You have misinterpreted and misapplied Romans:12:21. The context (vv. 17-20) is all about not acting in revenge against someone who has personally wronged you: "Recompense to no man evil for evil...avenge not yourselves...if thine enemy hunger, feed him...." This is one way we are to overcome evil with good.
As for being an overcomer in an evil world, we are told: "...this is the victory that overcometh the world, even our faith" (1 Jn:5:4). I find neither command nor example in Scripture calling me to engage in social action to help unbelievers "overcome" any evil on this planet.
Neither Christ, the apostles, nor the early church led or participated in any public protests against any evil practices, though evil of all kinds (including abortion) was rampant throughout the Roman Empire in their day. Christ commanded us to go into all the world to preach the gospel, which calls men to forsake the world and become citizens of heaven. He told His disciples: "...ye are not of the world, but I have chosen you out of the world" (Jn:15:18-20).
As reasonable as your view sounds from man's perspective, I cannot find one verse in the Bible to support it.