The Gospel is Culturally Neutral
Gal 2:14 When I saw that they were not acting in line with the truth of the gospel, I said to Peter in front of them all, "You are a Jew, yet you live like a Gentile and not like a Jew. How is it, then, that you force Gentiles to follow Jewish customs?
What they were doing was not in line with the truth of the gospel. One aspect of gospel truth is that to be a Christian you don't to have give up your cultural identity - at least concerning things not dealing with sin. The Jewish legalists had the idea that for Gentiles to become Christian they had to adopt Jewish customs - they were to get circumcised, not eat certain foods, dress a certain way, observe certain days. These things are not relevant to salvation. "For the kingdom of God is not a matter of eating and drinking" Rom 14:17
As Christians we need to consider how we might inadvertently be misrepresenting the gospel, as for example in making Christian fellowship contingent upon cultural conformity.