Okay, here goes. (Deep breath...)
- The story of Sodom and Gomorrah (Genesis 19) is about gang rape, not about monogamous same sex relationships.
They've got the chronology all mixed up. The destruction of the Sodomites was planned BEFORE they ever saw the angels, lusted after them, and tried to break in Lot's house to gang-rape-sodomize them. That story tells just how very wicked they were. (Why, they wanted nothing to do with Lot's daughters!)
- God, who knows the human heart, testified to them by giving them the Holy Spirit, just as he did to us; and in cleansing their hearts by faith he has made no distinction between them and us. (Acts 15:8-9)
They skipped over a verse: "Peter rose up, and said unto them, Brethren, ye know that a good while ago God made choice among you, that by my mouth the Gentiles should hear the word of the gospel, and believe." (Acts 15:7) Now we know who the "us" and "them" are.
- Marriage is honorable for all, and the marriage bed undefiled
What is marriage? An arrangement invented by man? No, it was created by God:
"And he answered and said, Have ye not read, that he who made them from the beginning made them male and female, and said, For this cause shall a man leave his father and other, and shall cleave to his wife; and the two shall become one flesh? So that they are no more two, but one flesh. What therefore God hath joined together, let not man put asunder. - Matt. 19
Or know ye not that he that is joined to a harlot is one body? for, The twain, saith he, shall become one flesh. - I Cor. 6:16
In the past, our laws provide for annulment if the marriage had not been or could not be consummated. And we all know what "consummated" means. A "marriage" between two people of the same sex cannot be consummated. They can never become "one flesh".
- There is no longer Jew or Greek, there is no longer slave or free, there is no longer male and female; for all of you are one in Christ Jesus. (Galatians 3:28)
Are they seriously suggesting that we're all androgynous now? ("let the women keep silence in the churches" I Cor. 14:34) That slavery disappeared from the Earth? ("Servants, be obedient to them that are your masters according to the flesh, with fear and trembling" Eph. 6:5) That racial/cultural differences faded away? ("And he reasoned in the synagogue every sabbath, and persuaded the Jews and the Greeks." Acts 18:4) They haven't read Galatians very carefully, so they've missed Paul's point altogether.
- The Romans passage (Romans 1:26-27) is describing idolatry leading to same-sex sexual rituals, not homosexuality in general (read the entire chapter, not just verses 26-27).
So because the path to this abomination is described, it's no longer an abomination? Is murder okay as long as I'm not sacrificing the victim to Molech?
being filled with all unrighteousness, wickedness, covetousness, maliciousness; full of envy, murder, strife, deceit, malignity; - Rom. 1:29
Are these things sinful only for idol-worshippers?
- Then we have the problem of translating the terms arsenokoitai and malakoi in 1 Corinthians 6:9 and 1 Timothy 1:10. No one really knows what arsenokoitai means because Paul coined the term. Many gay-marriage-affirming Christians believe this is harking back to the Leviticus passages and thus refers to those participating in pagan same-sex sexual rituals.
What problem? Arsenokoitai is a word coined by combining two words, yielding the new word "male-bedders". Malakoi means "soft" or "effeminate". The Bible writers often used euphemisms ("lie with", "know", "cover one's feet", etc.), just as we do ("sleep with", "powder one's nose").
You don't have to know many same-sex couples to observe the natural male-female relationship in its perverted state: One plays the male part, and the other plays the female part. (Pardon my bluntness, but if they both played the same part, they'd never get anywhere.) And the role-playing goes beyond their sexual acts.
They know this. They deny it, because it's a constant reminder of God's design of male and female which they fight against. (What exactly is "the natural use of the woman" in Rom. 1? What does it mean for something to be "against nature"?)
But God made men and women perfectly suited to their unique roles in marriage. When those roles are embraced and filled, showers of blessings fall from heaven. When those roles are abandoned, trouble ensues in the home.
Whew! I think that covers all the un-Scriptural arguments you cited from them.
So tell me, do you still need traditions? ;-)
If we follow the Holy Scriptures long enough that our obedient practices become "traditions", well and good. But we must never forget where those traditions came from, lest we start to rely on them as authoritative in place of the Scriptures. (I've seen this happen in churches in the space of just a couple generations.)
I believe my responses above are in accord with God's Word. But if I'm wrong, I sure hope someone will show me!