Confront the person with his manipulation. Remind him that it isn't your life he has to measure up to, it's the Word of God. Along that line, there is the idea that the gay sex drive is stronger than the straight sex drive. And that, as a result, gay persons have less ability to resist temptation, let alone stay celibate, than straight persons. This is a gross generalization purported by Christians and non- Christians alike.
Sin is still sin.
God's remedy begins with genuine repentance, confession, and acceptance of God's forgiveness. An ex-gay counsellor cannot help but make comparisons with his old life, drawing from personal experience. Often the ex-gay counsellor can find himself substituting personal experience for Biblical truth, and being limited by his own experience. He gives that individual a glimpse of life in the Body of Christ as it should be. The average lay person is not from a gay background.