There is an ongoing debate, usually involving religious or at least fundamentally religious individuals, about whether or not being homosexual is natural or not. We should probably presume that 'natural' here means either intended or good, with some individuals interchanging the two terms as if they meant the same thing.
There are two things to consider regarding this debate. One concerns the actual meaning of 'natural' and the other concerns the idea of 'offense', which is at the heart of why there is a debate about homosexuality in the first place.
What is natural?
To define something as being natural could at first seem problematic. However if you can think out of the box so to speak, and less emotionally, it could be somewhat of an easy question to answer. For many religious people 'natural' is defined by God's laws, or at least their understanding of what God's laws are. Although a straight forward idea this is not the one we are looking for.
The concept of natural really needs to be thought of as neither good nor bad, but as simply something that occurs. Perhaps we could say that 'being natural' is something that occurs in nature. But what is nature and what is not? Is it everything on Earth excluding human creations that truly define the idea of nature? Are humans now beyond the idea of 'being natural'? When did humanity leave the natural world - was a specific line crossed or is it mere subjectivity?
Most would agree that humans themselves are natural. They are seen to come from what we subjectively consider nature to be, but since inventing cell phones and nuclear missiles humans are now seen to inhabit an unnatural world, full of unnatural creations.
When a bird constructs a nest out of twigs, grass and mud is that also considered unnatural, or is it natural because the building materials are quite obviously from the soil and various flora (nature)? The thing that you must understand is that, like animals, anything that a human creates can only ever be created from material that comes from nature. This includes silicon computer chips and nuclear power.
Further arguments may suggest that humanity distorts natural material into something unintended and unnatural. This is judged by how dissimilar this creation is compared to something that, in our eyes, either God created, or naturally evolved without human interference.
The crux is that no matter what you believe, whether it's creationism or evolution, humans themselves came from nature - they are physically made up from natural material and their characteristics are formed by natural means.
Even if you were to say that humans consists of souls, you would still need to explain how they were unnatural compared to the contents of this blue planet. If a God created everything why would the planet be natural and the spirit world be unnatural if it all came from the same creative force? If you believe in a more naturalistic type of spiritualism, without a God, but still consisting of eternal souls, the same logic would still apply.
Where is the actual divide between natural and unnatural? The question that really needs to be asked is: what has truly formed beyond a natural process, whether we consider that to be material or metaphysical?
If aliens had come and altered humans from cave dwellers into what we are now you must still consider those aliens and their behaviour to be natural. They themselves (or even their creators) have formed in natural ways. Although they would have come from an unfamiliar and possibly vastly different world, they should still be considered natural, albeit alien to what we're familiar with.
This is not to say that we're the product of an alien intervention, it's merely to illustrate that anything that occurs should be considered natural because it has all come about via the same mechanisms. This applies to wether you believe God has created everything (nature), or if everything formed unaided by any supernatural or conventionally intelligent being/s.
Therefore whatever humans do can only ever be considered natural. Everything humanity has created has come from the natural world around them, including the forming of their ideas, dreams and behaviour. This is not reserved to what we consider good, acceptable or useful human behaviour. This includes ideas such as: kindness, cruelty, every type of sexual act, and any other behaviour you can think of.
People often confuse nature with being good, and anything bad or harmful as being unnatural. The truth is if we took humans out of this world completely it would still be full of pain, destruction and endless calamities. What we subjectively consider to be bad (destructive) and good (creative) has occurred before our arrival and will undoubtedly continue long after our existence on this planet.
There is another issue relating to the 'gay debate' and that has to do with the idea of offence. If someone is offended by a heterosexual couple kissing in the street in a fairly understated way, then this says more about the offended individual than the couple. It's the offended individual's weakness that has brought about such a feeling, which could be a rather deep-seated psychological issue relating to a negative or stifling experience in their formative years.
If the couple were kissing as though they were about to rip each other's clothes off, this may shine a poor light on the couple that needed to do this in the middle of the street. In this case many people would think it normal to be offended by such behaviour.
The truth is whenever anyone is offended it is because they are unable to emotionally handle what they are being offended by. Being offended is a (perhaps subconscious) recognition of a particular internal weakness, rather than merely recognising something external that is subjectively unpleasant. (The topic of why individuals are offended probably needs a whole essay of its own, if not a whole book to properly delve into this topic).
The reason for bringing up the idea that being offended is really a recognition of an internal weakness was not supposed to be directed at those that get offended by homosexuality. It is directed at the idea that any 'God' could be offended. This would suggest that God could not emotionally handle the idea of homosexuality, or anything else that God is accused of being offended by. If any God was truly offended by anything, this could only be interpreted as a weakness.
It's important to realise that being offended is not the same thing as recognising something that is actually negative to some degree. It is an emotional reaction, not an intellectual reaction. This is why the idea of being offended is separate to the idea of recognising something that is negative.
The reality is more likely that individuals project their own weaknesses upon their God, rather than their God actually being offended by anything. To say that is was 'written', usually in an ancient text, that God was offended by this or that behaviour still doesn't hold much water. The same projection of weakness can be applied to the writer and culture that any such text was written in.
If any such God was truly offended by gay people, or anything else for that matter (which would seem strange for any omniscient being), then surely they could smite the offenders out of existence? Surely this would be more effective than 'hoping' that mere mortals that were as offended as their God by homosexuality, will eventually sort out the whole 'gay conundrum'. So far those that are offended by gay people have been rather ineffective in curbing their homosexuality.
Claiming that God is in fact actively ridding the world of homosexuality is a claim made from flimsy evidence at best. The odd city flood, fire, or any other such disaster hardly seems like an effective way of eradicating homosexuality, especially for a being that is so very omniscient and apparently so very offended. These events are likely to devastate more heterosexuals than homosexuals. Saying that these heterosexual individuals must have supported gay lifestyles is a desperate and puerile attempt to justify their seemingly random deaths.
Surely the only conclusion is that either these Gods are sleeping at the controls, not even there, or not at all offended by any human behaviour, including: their varying religious practices, war, torture, environmental degradation, Western diets, reality TV or homosexuality (arguably the least harmful thing from these examples).