It's even harmful to those who aren't forced into the "conversion" programs. It promotes the notion that being gay is wrong/sinful/perverted/etc. It causes people to harbor hatred and resentment towards gay people. In turn those people can and do act in ways that harm gay people. They may verbally and/or physically abuse them or even kill them.
LGBT people who have that notion--that being gay is evil--may take that teaching to heart. They internalize it and suffer psychological/spiritual harm from it, particularly if they are religious and hear a lot of it at church. This can result in them suffering mental illnesses like depression or PTSD and even turning to drug use to cope with the pain. Suicide is not uncommon as an extreme end result of the pain inflicted by the dogma of the "Ex-Gay" movement.
Furthermore the "Ex-Gay" movement does everything in its power to prevent LGBT-rights legislation from being passed. It also works to get passed legislation that harms LGBT people, such as constitutional amendments banning same-sex marriage, laws that prevent gay people from adopting children, laws to prevent school children from even hearing that LGBTs exist and so on.
It's a hateful and harmful movement, and worst of all they try to claim they're acting out of love.
Some good sites that expose the Ex-Gay movement are:
http://www.exgaywatch.com/wp /
http://www.beyondexgay.com /
http://www.truthwinsout.org /
