Choice
What? Someone can't make their own decisions to change something about their lives? If the app can help someone make changes that they themselves want, then what is wrong with that? Do you really think that all homosexuals want to embrace their homosexuality? People think of you differently when you come out to them. It's not that fun to make friends with people and then have them suddenly treat you differently. If the app helps people become straight, then how about letting the person affected by this make the decision to download the app or not.
Don't ban the app. I will decide for myself if the app is discriminatory. If it is, then I can always delete the app from my phone. Saying that all gay people have to think that the app is discriminatory is just as bad as saying that all African Americans have to vote Democrat. Gay people can decide for themselves if they want to have this app and black people may vote for whomever they like.