People that claim to follow the teachings of Jesus, to love ALL, discriminate against those who choose to love a person of the same gender.
When people discriminate against a certain group of people they can inadvertently harm a different group of people who have no say in the matter. In the case of this ad, gays are the most eligible, and likely, to adopt orphaned children, since they cannot have children on their own. When gays are unable be married, they are unable to both become legal guardians, which can make the adoption process extremely long or even impossible.