Genesis 19:37 And the firstborn bore a son, and called his name Moab: the same is the father of the Moabites unto this day.
Genesis 19:38 And the younger, she also bore a son, and called his name Ben-ammi: the same is the father of the children of Ammon unto this day.
I see your ancient history and raise you the LAW, Leviticus 18:
[First the catch all]:
No one is to approach any close relative to have sexual relations. I am the LORD.
[Now some specifics for those that are slow:]
7 " 'Do not dishonor your father by having sexual relations with your mother. She is your mother; do not have relations with her.
8 " 'Do not have sexual relations with your father's wife; that would dishonor your father.
9 " 'Do not have sexual relations with your sister, either your father's daughter or your mother's daughter, whether she was born in the same home or elsewhere.
10 " 'Do not have sexual relations with your son's daughter or your daughter's daughter; that would dishonor you.
11 " 'Do not have sexual relations with the daughter of your father's wife, born to your father; she is your sister.
12 " 'Do not have sexual relations with your father's sister; she is your father's close relative.
13 " 'Do not have sexual relations with your mother's sister, because she is your mother's close relative.
14 " 'Do not dishonor your father's brother by approaching his wife to have sexual relations; she is your aunt.
15 " 'Do not have sexual relations with your daughter-in-law. She is your son's wife; do not have relations with her.
16 " 'Do not have sexual relations with your brother's wife; that would dishonor your brother.
17 " 'Do not have sexual relations with both a woman and her daughter. Do not have sexual relations with either her son's daughter or her daughter's daughter; they are her close relatives. That is wickedness.
18 " 'Do not take your wife's sister as a rival wife and have sexual relations with her while your wife is living.
And on and on. Animals are in there, too.
Is this some sort of Biblical slur?
The product of these abhorrent acts of sin were the Moabites and Ammonites, and they did not come to a good end. Lot's entire family is in the Bible as an example of sinful behavior.