Sin is a concept that only exists according to a theistic view of life. The concept of sin makes no sense if one looks at it from an atheistic viewpoint. We don't get our ethical codes from religious authorities that make proclamations about what is moral or not.
You're right, to say that man is "imperfect" makes no sense. What is perfect? Again, this only comes from a theistic viewpoint. Is a cat perfect or imperfect? What about a cow, a bird? We aren't the culmination of evolution which has created some sort of animal that can be "perfect".
There is no "sin" to get rid of. Again, that's just a theistic construct.
I participate in a big creation vs evolution, theist vs atheist discussion on a dutch forum, and it forces me to think and sometimes I think I get some interesting insights.
So I had just figured out that the concept of "sin" and that man is "imperfect" is totally not an argument against atheists, because "imperfection" implies a purpose. It is impossible for a human being to be "perfect".
It also follows that getting rid of sin is impossible, because if you don't have sin anymore you aren't human anymore.
Any thoughts?