Matthew 19:12 doesn't say people are born gay. This should help explain it.
"In Matthew 19:12, Christ describes three types of people as unfit for marriage, namely those who have been castrated (which all exegetes take as indicating eunuchs); those born incapable (con-genital eunuchs) and those who, by their own free choice and for the glory of God’s Kingdom, abstain from marrying (voluntary celibates)." -ajol
That's not true.
19 The two angels arrived at Sodom in the evening, and Lot was sitting in the gateway of the city. When he saw them, he got up to meet them and bowed down with his face to the ground. 2 “My lords,” he said, “please turn aside to your servant’s house. You can wash your feet and spend the night and then go on your way early in the morning.”
“No,” they answered, “we will spend the night in the square.”
3 But he insisted so strongly that they did go with him and entered his house. He prepared a meal for them, baking bread without yeast, and they ate. 4 Before they had gone to bed, all the men from every part of the city of Sodom—both young and old—surrounded the house. 5 They called to Lot, “Where are the men who came to you tonight? Bring them out to us so that we can have sex with them.”
6 Lot went outside to meet them and shut the door behind him 7 and said, “No, my friends. Don’t do this wicked thing. 8 Look, I have two daughters who have never slept with a man. Let me bring them out to you, and you can do what you like with them. But don’t do anything to these men, for they have come under the protection of my roof.”
9 “Get out of our way,” they replied. “This fellow came here as a foreigner, and now he wants to play the judge! We’ll treat you worse than them.” They kept bringing pressure on Lot and moved forward to break down the door.
10 But the men inside reached out and pulled Lot back into the house and shut the door. 11 Then they struck the men who were at the door of the house, young and old, with blindness so that they could not find the door.
12 The two men said to Lot, “Do you have anyone else here—sons-in-law, sons or daughters, or anyone else in the city who belongs to you? Get them out of here, 13 because we are going to destroy this place. The outcry to the Lord against its people is so great that he has sent us to destroy it.” -Genesis 19:1-13
You underestimate the average Christian.