Well, I asked for a quote and you gave me a quote, so thank you. I admit I'm not learned enough in this area to even try to explain it, (although I do note the breaks in text and the fact that the source is unfriendly to Luther's views.) However, it is what it is and I don't know the answer. The idea is just so strange to me that he would so openly refute something so plain in the Bible. I don't understand, I need to learn more about this.
This is nonsense that is perpetrated from not understanding what Luther is saying. Catholics believe that man is not all that bad. Consequently they can "work" themselves into better and better situation through communion, pentence, indulgence, etc. Luther is saying that man is rotten and nothing he does is going to satisfy God. However, although we cannot help but sin we have a redeemer who has taken care of these sins.
Catholics can't understand Luther's comment simply because they don't believe in original sin.