There's no nicer way to say this but...

[kılıç_mehmet]

You cannot scientifically remove ideas and thoughts.
Science will, one day, find the exact causes of homosexuality in humans.
And it will find a cure, even if people who think themselves above society, science and decency will oppose it while screaming "bigotry".

The 'cause' of homosexuality (and heterosexuality, for that matter) is likely not so simple. A combination of genetics, fetal development, and early environment probably all contribute to varying degrees. There will never be a simple 'cure'.

There is no cause of heterosexuality. That is the way things are supposed to be. The reason you have a penis and testicles is to use these for reproduction. It's the "default" type of sexuality, or it should be for every human.

If there are other factors that are incurable, they certainly can be taken into consideration, but one should eliminate the factors that one can before the child has reached a certain stage of development in the womb.

Unrealistic.
It was never implied adoption would solve overpopulation, the fact they can't have kids themselves would. As to the problem of surrogacy, discourage it. Not just to gay couples but to straight couples as well, encourage them to adopt instead. Adverts, billboards, it doesn't matter. As long as its being put out there that the kids need homes, make it look like the right thing to do. That a child doesn't have to have your genetic traits to be your son or daughter, it just needs your love. These aren't unreasonable concepts. Also, I think it highly unfair that you use Elton John as the standard by which all gay couples should be judged. Most of them have their own hair and everything.

Well, the only factor that discourages gays from obtaining children via surrogacy is the high costs and of course, the legality of the act.
Besides, adoption is likely to be a way for infertile couples to have kids.
Most people who are biologically able still continue to have children the old fashioned way. As I said, advocating adoption does not solve overpopulation, it never did, and never will.
Personally, I would consider adoption only in a case in which I'm very rich, and have the money to look after an extra child, as an addition to my biological children. I also encourage adoption for the children of our lands, but first and foremost of all, I encourage a planned family.
A planned family that follows and cherishes our good customs and qualities is what will drive us forward.
And I think it's only fair if I use a prominent gay person who has completed every objective that the current gay community aims to archive for themselves.

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The fact that homosexuality exists not just in humans, not just amongst the ape family of which human is a branch, not just amongst mammals, and not even just amongst the phylum that includes vertabrates, but in other phylums in the animal kindom such as the arthorpods as well, strongly suggest there is evolutionary pressure to preserve this behavior. This means any gene(s) reponsible for homosexuality is a well vetted, if perhaps subtle, evolutionary and survival advantage for the population that possesses it.

And how, might I ask, does homosexuality help for a population to survive?
For that to happen, homosexuality should only come forward in rather weak individuals, with little chance to reproduce other than by force, if they want to, as to drive them out of the genepool. I personally think it has little to do with the survival of the population.