Theologically, without hating someone that differs, a biblical Christian should avoid such a situation for the non-exhaustive reasons below:
1. If unmarried...fornication and adultery are considered sinful and evil.
Matthew 15: 19-20 New American Standard Bible
(NASB)
19 For out of the heart come evil thoughts, murders, acts of adultery, other immoral sexual acts, thefts, false testimonies, and [i]slanderous statements. 20 These are the things that defile the person; but to eat with unwashed hands does not defile the person.”
As long as I have been an academic, and previously, I have always readily admitted that with many people, at least, including self, sexual sin is a problem at the thought level.
2. A biblical Christian person, if married, should be married to a person of the opposite sex and to a Christian believer. See Romans 1-3, 1 Corinthians 6-7, 2 Corinthians 6.
3. I am not stating that people that do not follow a New Testament sexual ethic, do not have significant romantic love. I am stating that it is not within God's perfect will for sexual relationships. Final judgement of each person (Revelation 20-22) is up to God. But, I am prayerfully presenting New Testament theology, accurately.
4. An aspect of loving one's neighbour (Mathew 22, Mark 12, Luke 10) is to share biblical doctrine, accurately, in context, despite when it differs from modern, secular, standards. At the same time, within a democracy, within law and order, supporting the rights of others to live as they please.
