The gay rights movement (GRM) needs to reframe its argument for gay marriage. It should do this by taking back the powerful concept of "protection" which compels us to to find a victim and an oppressor.
In this case, through a slick slight-of-hand and plenty of outright untruths, the anti-gay marriage organizations picked their victim: children. They repeated this myth using various illegitimate arguments until people felt uncomfortable and threatened at any mention homosexuality. Once this emotional reaction was established, they could activate people's conditioned response with the word "protection" even if it was followed by two more words: "...of marriage."
This effect is likely stronger in parents. Consider the levels of early parenthood in the black and evangelical community. Could the large number of parents in their ranks account for their support for gay marriage bans?
The GRM only argued for protecting gays and left children out of their argument. But people care more about their children than anyone else. So the GRM should argue that we must protect our children from the ignorant and harmful beliefs held by the bigots. Gays who have internalized negative feelings about their identity have higher rates of depression and suicide than those who haven't. Hate crimes by the ignorant and intolerant against all minorities are on the rise. We must be able to pass on to our children a safer world, a society that doesn't indoctrinate intolerance but values diversity and liberty.

When protesting a church, put some bible verses on your sign:

(Romans 16:17)
Now I urge you, brothers, to watch out for those who create divisions and sinful enticements that oppose the teaching you have learned. Stay away from them

(Jeremiah (29:11)
"For I know the plans I have for you," declares the LORD, "plans to prosper you and not to harm you, plans to give you hope and a future."

(2 Timothy 3:16
"All Scripture is God-breathed and is useful for teaching, rebuking, corraecting and training in righteousness,"

(Matthew 5:10)
Blessed are those who are persecuted because of righteousness, for theirs is the kingdom of heaven.

(1 John 4:16)
And so we know and rely on the love God has for us. God is love. Whoever lives in love lives in God, and God in him.

(Romans 14:10)
But you, why do you make yourself your brother's judge? or again, why have you no respect for your brother? because we will all have to take our place before God as our judge.

(Proverbs 29:12)
If a ruler listens to lies, all his officials become wicked.

How to make a biblical argument for gay love:
God created gays, who are gay by their very nature. God only condemns going against one's nature. Unlike genes, a hard-wired attraction (maternal immune hypothesis) can't be flipped on or off. Since gays love, and whoever lives in love lives in God, gays live in God.
According to (Romans 1:29-32), whoever is full of malice and insolence, whoever disobeys their parents; and whoever is heartless, deserves death. Therefore, by indoctrinating your child to be insolent and heartless, no matter what they do they are sinning against God.