I'll say this right up front, this is the time of year for churches to have their synods (or whatever they choose to call them). And the issues comes around.
Polygamy hasn't (although a few years ago the denomination I was a part of made a decision that they would no longer call polygamy a sin - this was because in areas where polygamy is legal and/or common, they didn't want to tell a new convert he had to divorce a wife). The other two issues are very much around.
"Drinking alcohol is a sin".
Those who claim this (the new SBC resolution says not only the consumption of alcohol is sin, but also the manufacture and distribution).
These people would not only have kicked Christ out of the wedding at Canna, they would have forbid Him from performing His first miracle. I think that is somewhat of a quote that came to me from somewhere that I can't find now but the link was here.
"All divorce is sin."
God paints a "word picture" of Himself as a man who is divorced describes Himeself as being divorced. (Jeremiah 3)
"Polygamy is a sin."
God paints a "word picture" of Himself as a man describes Himself as having a covenant relationship with two wives, demonstrating the relationship between God, Israel, Judah.
There is a vast difference between how things originally were and what humans have made things to be.
Use of alcohol makes a heart merry. Abuse of alcohol destroys families.
Biblical use of divorce is unfortunate, but it is Biblical. And even an unbiblical divorce is not an unforgivable sin. Abuse of divorce leads to a nonchalant view of the marriage covenant.
Use of polygamy can (in certain circumstances) be used to solve population problems and work problems. Abuse of polygamy leads to abuse of women, jealously and strife.
We should be careful not to call "sin" what the Bible does not call sin.
We should also be careful to understand that even if the Bible doesn't call something "sin", what humans have done with it can be (and many times is) sin.
It is important to know the difference