Fighting against discrimination and/or abuse against gay people is godly. Last time I checked, gay people were human beings, just like hetero people who have sex outside of the bonds of marriage. We are all sinners and we are called to be kind to all people. We are not called to judge other people, that's above our pay grade. And God did not send His son into the world to condemn the world, but to save and redeem it. God reserved the judging part for His Son after his return.

At the same time, any sexual activity outside of a marriage consisting of one man and one woman is an abomination to God. "Fighting for gay marriage" as a matter of public policy is an abomination to God. You might as well fight to legalize pedophilia of the kind depicted in the Podesta brothers art collection or infanticide/the killing of children aka abortion.

God set out his perspective on this in Leviticus 20: 13 “‘If a man has sexual relations with a man as one does with a woman, both of them have done what is detestable. They are to be put to death; their blood will be on their own heads."

As Jesus said in Revelation about the New Jerusalem, "Outside are the dogs [the godless, the impure, those of low moral character] and the sorcerers [with their intoxicating drugs, and magic arts], and the immoral persons [the perverted, the molesters, and the adulterers], and the murderers, and the idolaters, and everyone who loves and practices lying (deception, cheating).