@Julia_Bracewell That is a great question and very relevant to our society. @CarsonWeitnauer recommended some great resources for delving deeper into how to engage culture on this difficult topic. I would like to suggest that perhaps you have the question upside down or backwards. The question is not ‘how do same-sex marriages result in unhealthy/bad lives?’ but rather ‘how does an unhealthy heart lead to slavery to our sexual passions to the point that we say no to God and yes to sex?’
In the Bible, as we see in Corinthians and Romans, we are slaves to whatever we obey and as even science will tell you, acting out on wrong sexual desires leads to addiction to them (sinning against your own body corrupts the mind). And as pointed out by Hollinger and Romans 1, idolatry in the heart - seeking our ultimate meaning outside of God - leads to sexual immorality. The issue here is one of idolatry and identity.
Tim Keller has a great sermon on ‘Counterfeit Gods’ and how they can control us / destroy us. So I would say that the negative consequences of living out wrong sexual desires is the same as any other form of idolatry - the destruction is wrought by the wall it creates between us and God and the dependence on idols that cannot save in the day of disaster or heal our hearts.
Now, a person may say that God is first in their life while they are living in contradiction to Scriptural sexual ethics, but the Bible is clear that anyone who tells God ‘No, I’ll do it my way on this one’ is a slave to their bodies - not to God. I will admit that there may be baby Christians or those on the edges of faith that really are trying to follow God in the midst of this state. In fact, in her testimony, Rosaria Butterfield says there was a time as she was on her journey towards God that she was still living with another woman, but there came a time when she realized she had to make a decision to continue drawing nearer and end that behavior or draw back. I would never want to place condemnation on someone who is trying to work out their faith sincerely, but I do believe firmly that those who seek the Lord’s will earnestly on this matter will come to it rightly in the end.
I think we would do well to remember both that we cannot serve two masters and that there is no sex in Heaven - our identity ultimately must be rooted in Christ or it will self-destruct, if not in this life, then in the age to come.
Are those thoughts helpful? Did I address the question? The Lord Jesus grant you wisdom as you seek to love your friends and to honor the Lord.
1 Corinthians 6:18 - Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body.
Romans 6:12-14 - Therefore do not let sin reign in your mortal body so that you obey its evil desires. 13 Do not offer any part of yourself to sin as an instrument of wickedness, but rather offer yourselves to God as those who have been brought from death to life; and offer every part of yourself to him as an instrument of righteousness. 14 For sin shall no longer be your master, because you are not under the law, but under grace.
Romans 6:16 - Don’t you know that when you offer yourselves to someone as obedient slaves, you are slaves of the one you obey–whether you are slaves to sin, which leads to death, or to obedience, which leads to righteousness?
“The link between idolatry and sexual immorality is established by the frequent use of ‘prostituting themselves’ or ‘adultery’ to describe Hebrew idolatry [in the Old Testament]. Israel’s unfaithfulness to God was not only a form of spiritual prostitution or adultery, but it also led to the physical acts themselves.”
Dennis P. Hollinger , The Meaning of Sex: Christian Ethics and the Moral Life , pp. 64-65
“What is an idol? It is anything more important to you than God, anything that absorbs your heart and imagination more than God, anything you seek to give you what only God can give…A counterfeit god is anything so central and essential to your life that, should you lose it, your life would feel hardly worth living. An idol has such a controlling position in your heart that you can spend most of your passion and energy, your emotional and financial resources, on it without a second thought…An idol is whatever you look at and say, in your heart of hearts, ‘If I have that, then I’ll feel my life has meaning, then I’ll know I have value, then I’ll feel significant and secure.’…If anything in life becomes more fundamental than God to your happiness, meaning in life, and identity, then it is an idol.” ( Counterfeit Gods , xvii-xix)