Most would agree that Galatians is Paul’s most offensive letter, and some (like myself, Philip Esler, and Mark Goodacre) think that Paul ultimately failed in Galatia. On the other hand, the text of Gal 3:27-28 is often seen as one of the most attractive things Paul ever said:
For all of you who were baptized into Christ have clothed yourselves with Christ. There is neither Judean nor Greek, there is neither slave nor free, there is neither male nor female. For you are all one in Christ Jesus.
Mark himself, for instance, says this statement represents Paul’s “more mature developed thought” when compared to what he thinks is an earlier version of the formula in I Cor 12:13 lacking the “male/female” part. In the past I’ve been inclined to see the movement in the other direction — that Paul later dropped the “male/female” part of the formula out of sensitivity to emerging controversies over women’s roles in the church (I Cor 11:3-16). We know that he later dropped the entire formula in Rome, realizing that distinctions between Judeans and Greeks were important after all. As I mention in my Romans commentary/outline,
“In Galatians Paul says that baptism results in the abolition of ethnic boundaries: ‘in Christ there is neither Judean nor Greek’ (Gal 3:27-28). In Romans that’s the last thing he wants to say. Here the lesson drawn from baptism (Rom 6:1-15) is not the abolition of ethnic boundaries, rather just the opposite: Greeks escape the power of sin (Rom 6:16-23) in a completely different way than Judeans (Rom 7:1-25). Greeks die to ungodliness — that is, to “impurity and lawlessness” (Rom 6:19) — and then become slaves of God (Rom 6:22). Judeans die to the law (Rom 7:4).” (See Philip Esler’s Conflict and Identity in Romans, pp 218-219)
Gal 3:27-28 was as theologically offensive, immature, impractical, and doomed to fail in the real word as anything else Paul said Galatians. It was as bad as claiming that Abraham was the ancestor of Gentiles (Gal 3:6-9); that the law was an active agent consigning Israel to sin (Gal 3:19-26); that Judeans were illegitimate descendants of Hagar (Gal 4:22-5:1); that the Christian movement was now Israel (Gal 6:16).
Gal 3:27-28 appeals to my own modern Unitarian sensibilities, and it evidently appeals to Mark too. But historically it was more apocalyptically naïve, and offensive, than “theologically mature”. Paul’s world was one in which different ethnic groups, genders, and social classes could get along only by preserving their identities rather than eliminating them. (Attempts to eliminate actually encourage groups to re-assert their identies in overly aggressive ways, especially in competitive honor-shame societies.) Paul “matured” by gradually relinquishing the formula of Gal 3:27-28. It’s the last thing he wanted to say in Rom 6:1-7:6 — where in the context of baptism he went out of his way to assert differences between Judeans and Greeks — and indeed in the entire letter of Romans, where he shows greater sensitivity and maturity than perhaps ever before.