From what I read in letters to the editor and newspaper articles, there appears to be a misunderstanding that according to the Bible, marriage between a man and a woman is tradition, has always been that way and therefore should stay that way.
In fact, there are a number of rules regarding human relationships that at one time were supported by the Bible that society no longer supports:
1. We no longer stone a woman to death if she is not a virgin at marriage (Deut. 22: 13-21).
2. We no longer practice polygamy (Gen. 4: 19, 16:3, 21: 1-13, 25: 1).
3. Men no longer have concubines and slaves in marriage (Gen. 25:6, 30: 4, 30: 9). It is interesting to note that Solomon had more than 1,000 wives and concubines (Kings 11:3).
4. We accept interfaith marriages (Num. 25:6-11, Deut. 7:3, Ezra. 9:2-12, 10: 2-3 and Gen. 24:3-4).
5. We accept interracial marriages (Num. 12:1, Exodus 34: 12-16, Deut. 7:1-4).
6. We now have divorce and annulments as common practice (Matthew 5:32, 19:8).