In ex-gay ministries, gay counselling organisations, many people have reported that they still carry sexual urges towards the same sex. But they either claim that they only have 1% of the urges they used to have in the past, or tried to suppress the urges they face. They still carry homosexual traits after counselling and self-motivated "changing".

Suppressing homosexual urges does not necessarily prove that homosexual behavior is genetic and normal. The word you use is "many" not "all." Unless you can conclusively prove that all homosexuals still carry homosexual urges right after treatment, then it is possible that the treatment is not complete in unsuccessful cases and that more treatments are necessary.

In the movie A Beautiful Mind, John Nash suppresses his schizophrenic hallucinations even after treatment. He was not curable. Do we regard his uncurable schizophrenic condition as normal behavior? Of course not.

Yeah, but if you want to insist that homosexuality does not have a genetic basis, you'd have to show that all of them are "nurture" homosexuals. My feeling is that there are some who are "nature" and some who are "nurture".

Now just because we can show that some homosexuals are not genetically predisposed towards homosexuality (but for all you know they might be bi -> hetero), it doesn't prove that all of them are "nurture" homosexuals.

Also, it could be possible that homosexuality is "nurture", but once you start being one, it's irreversible. For example, if you are a heroin addict, and you never kick the habit, does it mean that you were born with an opiate addiction?