2. Men and women are anatomically different. They were created different for a reason. They are meant to complete each other not only physically, but also emotionally and spiritually, but above all to pro-create, two "gay" people can't do that. The Bible says that in the beginning God created them male and female and it is for this reason that a man shall leave his father and mother and cleave to his wife and the two shall become one flesh. That can never happen with two people of the same sex. It's impossible.
3. God is the author of marriage. He defines what marriage is, not the culture. And God defines marriage as the union of one man, one woman - not one man, one man; one woman, one woman; one man, several woman; one man, one beast or anything of the sort.
4. Marriage is a picture of Jesus Christ, the bridegroom and of His people (the church), the bride. "Gay marriage" is not biblical and is a perversion of this picture.
5. Being "gay" is a choice. There is no scientific evidence to the contrary. It is a behavior, albeit a sinful one. Sin is always a choice.
Homosexuals need to repent (turn from their sins) and put their trust in Jesus Christ as Lord and Savior, otherwise they will stand condemned before a just and Holy God on judgement day. They will spend eternity separated from God in a place of conscious torment, a place the Bible calls Hell.
The Bible says that all have sinned and fall short of the glory of God. There is no one righteous, no, not one. Likewise, you too will perish unless you turn from your sins and trust in Christ by faith as your Savior and Lord!
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