k) RESULT from the NEW TESTAMENT
Christians have always regarded monogamy as the only viable form of a relationship between husband and wife. In Christianity marriage is instituted and ordained by God as a life long relationship between one man and one woman. It must be kept pure. (Hebrews 13:4) And the condition of divorce in Christianity is adultery (Matthew 19:3-5, Mathew 19:6). However, the New Testament does not explicitly condemn one man being married to more than one woman, and polygamous men are not commanded to divorce any of their wives in the New Testament.
This shows us the second source of the diversity of opinions in the matter.
a) Basing an argument, for a former Muslim to keep his multiple wives, on Christ's interdiction of divorce, is tricky, because Christ allowed divorce in the case of adultery and from the point of view of biblical monogamy polygamy can be viewed as adultery (any additional woman breaking the marriage of the husband with his first wife). Therefore the arguments usually focus on other aspects:
b) Those, who suggest that polygamous converts SHOULD separate from their wives, focus on the deep spiritual truth revealed in the New Testament about a monogamous marriage being modeled after Christ's relationship to his church, for which he was ready to sacrifice his life. I believe this is the reason, why Paul demanded of ministers in the church to be married to one woman only.
c) And those, who suggest that polygamous converts SHOULD NOT separate from any of their wives, take advantage of the lack of any commandments in the New Testament that husbands with more than one wife should divorce some or all of their wives.