There are a lot of straight people that are as wrapped up in sexual immorality as any gay or lesbian. In fact I would be willing to bet there is a fair share of "devout" Christians who view porn on a regular basis, and who are committing sexual immorality in their marriages, both men and woman.
Our bodies are our temples, created and gifted to us by God, after His image. To defile it in any way is sinful. The bible says it is the only sin in which we sin against our own body.
Gays and lesbians, and any sexually deviant behavior between a man and woman is an insult to God. With that type of conduct, the participants are saying that they are going to use their body in a rebellious fashion, outside of how God designed our bodies, and absent of love. A man with a man, a woman with a woman, and a man and woman doing things that God not intend for our bodies is something other then love. The act as intended by our Lord was to be a expression and gratitude of love. If one is doing something outside of Gods approval, doing something that God had not planned when He created us is sin.
So from a spiritual perspective focusing on the sinful endorsement by our government of gay marriage just punctuates the elements which prompted the discussion, the legal endorsement firstly, i.e., like the government permitting porn on the internet, licensing sex clubs and prostitution, the commercializing of sex by Madison Avenue and the entertainment industry, and the legalizing of abortions in the early seventies, sites like Ashley Madison that are pulling huge numbers. Lets not deny it, there are a portion of Christians who are involved in these things.
We're supposed to be the salt and light.
The implications of multiple sex partners and sexually deviant behavior become apparent as one becomes more experienced in life, and their walk with Jesus deepens. Thank God that He can and is willing the reverse and repair a lot of the damage inflicted on the soul, mind, and body; He restores the time the Canker worm and Palmer worm have eaten.
But the scars remain, to one degree or another.
The legalizing of gay marriage was just the next logical footstep in a public exhibition of what the outspoken and media controlled liberal culture has already yearned inwardly. Sin destroys, and in its desirous lust and selfishness will seek to seduce and /or devour anything, anyone, and everything that stands in its way.
The direction we are headed, gay marriage will one day seem relatively tame. I don't even want to discuss here what the next frontier of publicly endorsed sexual immorality may possibly be. Don't be naive to the possibility. It is already being openly discussed in France.
If we as Christians had not compromised ourselves to the degree we have, if we had not grown so comfortable in our materialism, if we had prayed and studied the bible more, and done more to spread Gods word, society may not be where it is today.
Unless it was a rhetorical question, as a conversation starter, to suggest that a Christian could even consider for more then maybe a moment if he or she could endorse gay marriage is outside the bounds of our manifest.