Bottom line, if man wasn’t intrinsically evil, why would we need a Savior? At most, we’d need a guidance counselor...and I don’t recall Mrs. Jenkins from 10th grade getting nailed to a cross to point me on the right path.
Actually, that’s one of the tenets of the “man is basically good” crowd - “there are many ways to God, not just Jesus”.
I seriously don’t see how you can justify calling yourself a Christian, saved by His sacrifice on the cross, then saying it wasn’t necessary.