"Flee from sexual immorality. All other sins a person commits are outside the body, but whoever sins sexually, sins against their own body." 1 Corinthians 6:18 (NIV).
In the Greek it reads like this:
"φεύγετε τὴν πορνείαν· πᾶν ἁμάρτημα ὃ ἐὰν ποιήσῃ ἄνθρωπος ἐκτὸς τοῦ σώματός ἐστιν· ὁ δὲ πορνεύων εἰς τὸ ἴδιον σῶμα ἁμαρτάνει" -Stephanus Textus Receptus 1550
"Every other sinful act (ἁμάρτημα), if it has to do at all with the body, works upon it from without, and consequently holds a position in reference to the body external to the same. The sinner makes that which is not of the body, but outside of it, as e.g. food and drink, to be the instrument of his immoral act, whereby the ἁμάρτημα, viewed in its relation to the body, comes to stand ἘΚΤῸς ΤΟῦ ΣΏΜΑΤΟς, and has there the sphere of its occurrence and consummation." -Meyer's NT Commentary.
Obesity is a medical condition which negatively affects a person's physical health but does not corrupt their soul and spirit. Homosexuality is a grave spiritual transgression which corrupts a person's soul and spirit.
Overweight people can certainly live moral upright godly lives fulfilling Christ's instruction to be His witness as salt and light in society.
Sexually immoral homosexuals whom are deceived by the devil are not living moral upright godly lives fulfilling Christ's instruction to be His witness as salt and light in society. Their lives reflect the unclean corrupt state of their hearts and minds with spirits in an unregenerate state of rebellious enmity toward God's own holiness [Roman 8:7] (or alternately if they were ever genuinely saved then suffering conscience which comes from grieving God's Holy Spirit and they are in desperate need of genuine repentance).
So no, just the opposite is true. Homosexuality is by far the greater danger to any society because it corrupts, deceives, and hardens the hearts, minds, and spirits of society's members against creator God and His holiness and subsequently society's government and institutions.
Obesity is a medical problem that doesn't corrupt, deceive, and harden against God people's hearts, minds, and souls and subsequently society's government and intuitions.
It saddens me to see professing Christians, like yourself, unable to understand the obvious and falsely assert the exact opposite.
I'm not saying that the insitute of gay 'marriage' couldn't undermine society, but isn't (the sin of) obesity (at about 0:08) a much greater danger to amercian society than homosexuality?