.the simple answer is that they can not. The detailed answer is that no one is gay, that is like a driver of a car, he is only a driver when he is driving. Such is with gays, they are only gay when they are engaged in gay behavior.
Leviticus 18:22 Homosexuality is an abomination and a sin...the two shall be put to death.
18:2 ...incest is a sin and man shall not lie with kin folks.
18:20-24...sex with animals, women are periods and children.
How can people continue the choice of gay behavior?
If we are truly "born again" then we are in Messiah. As long as we are in Messiah, G-d does not see our sin. Although this is a complex issue we are forced by time and characters to limit our posts. Once we become born again we continue to sin and constantly need the grace of G-d to remain in him. We are commanded to be filled with the Spirit so we will not satisfy the lusts of the flesh, but no believer in Messiah is constantly filled with the Spirit and falls into sin.
The sin of homosexuality is no less deadly than gossip, lying, stealing, etc.
If you are "born again" and struggle with any sin:
1Jn 2:1 My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:
First we are encouraged to sin NOT, but if we do he is faithful to forgive us if we are truly repentant. Don't be discouraged and think G-d does not love you, but get up and back in the race. G-d knows your weaknesses, he is not surprised or disappointed. He wants to change you from within in his time. Submit yourself to him and trust he will mold you into the person he created you to be and meet all your needs.