We do not all have to become the same, or conform, in order to have unity. Unity is the fitting together of different parts in a way that enables us to compliment each other, to be more complete, and to show the bigger picture. When God first instituted the church, He brought together two very different groups of people, the Jews and the Gentiles, and made them into one body. Gentiles did not have to become Jews and Jews did not have to become like the Gentiles. Each was able to retain their own individuality.
True unity transcends differences.
In reality, true unity comes out of diversity. When true unity exists, differences become irrelevant. Who we are in Christ is most important. We begin to live on higher principles. The source of unity comes in accepting one another just as Christ accepted us.