Forewords
We should preach full gospel and what God wants for people, e.g. how should Christians live and behave for His glory. And that's it. The problem comes when things don't go in an ideal way, then we have the responsibility to look into details and find right answers for each situation.
But my claim is, that we simply do not have detailed answers for each situation, and God did not intend us to be all-knowing. If someone says those are things Bible teaches simply and plainly, OK, no problem. But when certain situations arise which these Bible passages do not actually discuss, then it is more or less a stretch to apply certain passages to certain situations. That is called interpretation, which we all do. Then it is a matter of the principles by which we interpret.
Issue 1
All these are kind of background thinking and ways of seeing things. If we talk about re-marrying issue, the first point: what happens to the marriage covenant when divorce takes place. Let's assume the case to be, that one side wants to divorce (not-real-Christian) and the other side doesn't want (real-Christian). In Finland divorce takes place when one side wants it, so it happens.
- Is the marriage covenant broken or it is still valid? This is talking in spiritual world, because legally it is broken and that's over.
- One can argue that Bible teaches that this covenant is still valid and real-Christian performs adultery if re-marries, how can this be proved by Bible? Places such as Matthew 5:31-32, 19:9, or 1. Cor. 7:10-11 do not forbid re-marriage, they only state the desire of God that marriage should not be broken. Actually Matthew passages provide an exception to allow re-marriage (which is that the not-real-Christian performs adultery and the real-Christian can re-marry).
- Conclusion: I think "correct" re-marriage is not living in sin. Please don't think I "accept" any kind of re-marriage, human lives are not black-and-white, and different people tell different stories. I refer only to the above mentioned specific case. There are many many different cases in this world, sad but true.
Issue 2
When reading the Bible, into which context do we read Bible passages? If we read the words of Jesus, they were said in certain situation to certain people, we should understand what Jesus wanted to say to those people in those situations. Otherwise we read into His words with our ideas and thoughts. So here just raising this issue, please consider it.
Issue 3
Romans 1:24-26, the passage starts with word "therefore", meaning that they are referring to previous verses (18-23), where it is clearly talking about people who do not fear God and have become fools. Bible does not say God gives up on believers, rather, Bible confirms that God does NOT forsake anyone who comes to Him (e.g. Hebr. 13:5-6, John 17:12). It is only us people who can choose to abandon our faith and abandon Christ, and that's what the letter to Hebrews really warns us about: 3:12-14, 6:4-6. Also Matt. 13:3-8 and Romans 11:17-22. So God never gives up on us, but He allows us to leave Him is we choose to. (I know this issue is debated in theology, but here I'm just trying to make the point: God does NOT forsake anyone who comes to Him)
Issue 4
Matt. 7:22-23 is more tricky, because we as people, how can we know who are really known by Jesus and who are not? Actually, it's more about who really knows Jesus and who doesn't. It is an essential point that God is not only about love and mercy, but He is certainly a God of judgement and justice. Many people, who call themselves Christians, do not want to see this side of the coin, that is sad. Actually in Matt. 7 context, Jesus discusses exactly this issue, His theme being "recognize the tree by its fruit". We can recognize people by their fruits, BUT it is often very hard to tell, especially if outwardly everything seems to be so well (as in 7:22-23). Then again, we are NOT called to judge or to know other people's heart, what Jesus said to Peter in John 21:22 applies also today: let us follow Him, and He will judge all people.
On the other hand, it is of course our responsibility to preach the full gospel and warn our brothers and sisters who are going the wrong direction, in addition to waking up the sleeping believers and calling out to the lost people. All these must be done based on God's love, not based on us being right and others being wrong. The hardship lies: how to communicate love while telling the truth? It is not as simple as listing the Bible places and stating the truth. If we really act responsibly, we first make sure that we have the loving attitude, and then we pray Holy Spirit to guide us to say and do the right things. Often the respondents do not turn from their ways, then we are like the prophets of the Old Testament: Isaiah 51:1 (Romans 10:16).