A sense of accomplishment and victory.
...by undermining, redefining, and ultimately destroying the God-given foundational unit of western civilization, marriage and family.
As it was in the days of judges:
Judges 21:25 In those days there was no king in Israel: every man did that which was right in his own eyes.
These people desire to call what they do "marriage", as an ultimate perversion and defilement of the normal order of human existence. Same reason the definition of "family" has been hijacked, and not just by homosexuals.
Not an accident that sodomites pilfered the well-understood symbol of God's covenant with the earth and Noah. They can wave their rainbow flags all day long, believing that the Lord will not destroy them, but they forgot about what happened in Sodom: it was a "flood" of fire and brimstone that leveled the city.
Sodom = "burning", in more ways than one.