The way I have seen it best expressed, is that an unbeliever might perform a good work, but not good by Divine Standards. So when the Book of Works is opened up at the Great White Throne Judgment, those works not performed through faith in Christ, will fail to meet His criterion of righteousness, and His righteous Judgment will not accept them as evidence of righteousness.
Likewise, accepting the works performed as good independent of Christ, in order to find a common ground to plant the seed, can merely exacerbate future problems.
It can promote legalism, vice grace. A person’s mind is shaped by his thinking. As we solve problems independent of Christ, we scar our soul for future problem solving. If we continue to entrench our thinking upon what is right in our own eyes, we trend towards thinking independently of Him in the future. It becomes a stumbling stone to those not yet in faith with Him.
Problems? By following God's Will?