This whole thing is a process. I think that maybe Paul did not want to discourage us, so he is showing us the process. Thus, what looks like it might contradict does not, it's just a different step in the process. That's why Paul says he will show himself as certain things to certain people. He shows himself a Jew to the Jews. Well, he was a Jew in the process but now he considers that and all his claim to self-righteousness so much dung. So, he's not deceiving others, he is giving them a place to step on the ladder which they might not otherwise do if they felt condemned or rejected while still tender shoots.
Likewise, we start out with the law which condemns and end up with grace which makes us perfect.
7For if that first covenant had been faultless, then should no place have been sought for the second.
8For finding fault with them, he saith, Behold, the days come, saith the Lord, when I will make a new covenant with the house of Israel and with the house of Judah:
9Not according to the covenant that I made with their fathers in the day when I took them by the hand to lead them out of the land of Egypt; because they continued not in my covenant, and I regarded them not, saith the Lord.
10For this is the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people:
11And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest.
Just because we start out with a sin nature doesn't mean that is the goal, or that will be with us forever. We just have to stay on the right path.
1 O foolish Galatians, who hath bewitched you, that ye should not obey the truth, before whose eyes Jesus Christ hath been evidently set forth, crucified among you?
2This only would I learn of you, Received ye the Spirit by the works of the law, or by the hearing of faith?
3Are ye so foolish? having begun in the Spirit, are ye now made perfect by the flesh?
4Have ye suffered so many things in vain? if it be yet in vain.
5He therefore that ministereth to you the Spirit, and worketh miracles among you, doeth he it by the works of the law, or by the hearing of faith?
6Even as Abraham believed God, and it was accounted to him for righteousness.
7Know ye therefore that they which are of faith, the same are the children of Abraham.