Typically, when I think of the "and such were some of you" passage, the sins I associate with that phrase don't include having grievances against my brothers and sisters in the church. But that is exactly what Paul is talking about here. Granted, he is also transitioning to speak more about sexual immorality in the next passage, but the fact that he is tying this back to the greviences passage was a new understanding and brings the whole priority of the peacemaking process to a new level.
1 When one of you has a grievance against another, does he dare go to law before the unrighteous instead of the saints? 2 Or do you not know that the saints will judge the world? And if the world is to be judged by you, are you incompetent to try trivial cases? 3 Do you not know that we are to judge angels? How much more, then, matters pertaining to this life! 4 So if you have such cases, why do you lay them before those who have no standing in the church? 5 I say this to your shame. Can it be that there is no one among you wise enough to settle a dispute between the brothers, 6 but brother goes to law against brother, and that before unbelievers? 7 To have lawsuits at all with one another is already a defeat for you. Why not rather suffer wrong? Why not rather be defrauded? 8 But you yourselves wrong and defraud—even your own brothers!
9 Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, 10 nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God. 11 And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.