That last word, "unbelievers" is of key importance. A Christian should not marry a non-Christian no matter how kind and good they are.
Interracial marriage in the Bible
What about interracial marriage? Deuteronomy 7:1-6 tells the Israelites to destroy all the inhabitants of the Canaan land and not to intermarry with them because they would "turn your sons away from following Me, that they may serve other gods." The same key concern of 2 Corinthians 6:14 is again expressed here.
Moses' wife was of another race and in Numbers 12:1-15 Aaron and Miriam were punished for criticizing this interracial marriage. The book of Ruth tells a delightful story of a foreigner who became part of the lineage of Christ. The harlot, Rahab, also of another nation, is included in the lineage of Christ as recorded in Matthew 1. Colossians 3:11 makes it clear that from God's perspective all are one in Christ.
Interracial marriage considerations
The Bible is clear that when both parties are believers (equally yoked), interracial marriage is not wrong. A Christian couple contemplating marriage must prayerfully and carefully consider the impact their marriage will have within their cultural context, their family relationships, future children and the society in which they live. A loving Christian couple may accommodate well to many kinds of differences between themselves. However, there are cultural contexts where interracial marriage poses significant barriers to acceptance of the marriage and/or the children of the marriage.
Interracial marriages are becoming more common in many societies. All couples contemplating marriage need to give thoughtful consideration to a variety of practical issues, some of which may have no clear Biblical imperative.