I personally believe this is a very personal topic, for obvious reasons, the subject itself being #1.

The Danger of Shaming this M, as the word is not in the bible, there are groups that God asks not to remarry, those that are divorced that are not free to remarry according to scripture, those that are single & have not yet found a spouse, those that are not of age to marry. We all have CHOICES to make in life. That is why God Gives Free Will.. YES.
We CHOOSE. I would say that fornication IS sin because the bible says it is a sin. Lust IS a sin. Adultrey IS a sin.
M, is not in the bible.
One can turn on the tv & commit, "lust," or walk down the street & lust. It is retraining the self to not lust.
Fornication is a CHOICE. One chooses to fornicate. That's a sin.
Adultrey is obviously sin. It's wrong, Not of God.

I believe this topic is Very personal & as is life in general one must use discretion in their actions & work to please GOD.