Actually that's a good question...and probably one reason for the survey results.
Since every person is made in God's image we all have some "good" in us. However, since every person (past, present, & future) except Jesus Christ, is poluted by an inborn fallen sin-nature....being descendent of Adam, no one is purely good, which, by older definitions is the only kind of moral good...totally pure. Evil is the pollution of good...hence by that definition anything evil is partly (or even basically) good...however also BASICALLY polluted (and therefore evil) in every capacity...even in the ability to reason, desire and choose.
I think a lot of Christians if they understood that, would agree that everyone is basically a sinner....still with some "good" in us, but only in a relative sense. No one, save Christ, is purely and basically Good, in that sense.
This is a basic Augustinian understanding of the nature of good and evil.
Augustine had it wrong. He even mistranslated parts of the original fall. The Eastern Orthodox Church has many fundamental differences with his understanding.
Many Eastern Orthodox Theologians believe that Augustines writings play a significant role in the eventual demise of the West, including the necessity for Papal Infallibility, the Protestant fragmentation, and, played to its eventual end, agressive Atheism (since the rational mind confronted with conflicting mistruth will falsely accept one, the other, or reject them both).
See http://www.orthodoxpress.org/parish/river_of_fire.htm for a very good, yet short explaination of this problematic paradigm between EO and Western Theology.