The purpose of sexual organs is one of reproduction. In the animal kingdom reproduction is the motivation to exist. Thre are unicellular life forms that reproduce by simple spliting into two cells, and then subsequently cells divide and divide.
There are the hermaphrodite life forms, like the snails and some fish, where each representative of the species has both sex organs, female and masculine. Still, they need the intervention of a second animal of their species to fertilize, there is no self fertilization , although they can assume a female or male posture a they see fit.
There are the species that have clearly separated males and females. In these species the male and the female are created with specific aparatus to peform in a specific way to attain natures goal which is procreation, reproduction, the survival of the species.
In non inteligent animals...
( assuming human beings are the inteligent ones, although several species have demostrated a level of inteligence that is substantial, i.e Chimpanzees, Gorillas, Dolphins, Dogs, etc, there is levels and levels)...
... operate under the principal of estrous, seasons, hormonal changes that happen at the right time of the year, and only at the right time, to avoid having babies born in the chill of winter, in the dry months of the year, in the low food seasons, etc ( depending on the area of the globe).
Homosexualism is not a planed behavior nor a goal of nature. It serves no purpose. In the animal kingdom there is no sex beyond the mating season ...( except in captive or domesticated animals that lost their natural seasons and behavior due to corraling, or, artificial situations, like dogs, cattle, etc.)
... and in the animal kingdom there is no use for homosexuality. Cases of homosexuality in animals include many times a juvenile individual that has not yet developed a mechanism ( psycological) to reject or to seek females / males. There is no penetration of males by males, no oral sex performed by a male on a male , nor anything that many times humans want to athropomorphize on other species.
In our case, human beings, we have gone beyond any estrouses or seasons because we have learnt through our intelect to go beyond those natural barriers due to the fact that we can care for babies in any season, in any condition. We learnt to do away with seasons and estrouses before we learnt how to become a civilized society. Since nomadic times humans have chosen to have sex beyond the natural barriers mating seasons used to represent.
No animal goes beyond their seasonal clock, you will not see babies born in the winter in cold climates, you will not see babies born in dry seasons in the african deserts, you will not see baby pelican birds born in low fisheries seasons. Sex in only the means nature has found to asure the reproduction of species. If we had to work hard and stress out in order to reproduce and have sex, we would not do it. It has to be an enticing proposition.
Said that, again, and to no offense, homosexualism is not the intention of nature. It is an accident. Homosexualism is due to many causes, exposed baby brains to hormones the mother has taken during pregnancy, hormonal imbalances other than the brain, and psycological factors brought up by enviroment situations.
I know of a sad case were a guy at school, who was not gay, was teased and teased about being gay to the point that this guy was so disturbed that he ended up being gay. I remember being one of the guys that kept defending him, telling the others to leave him alone. Unfortunaltely, kids at teen times can be very mean, and this kid was steered into something he was not supposed to be. Years later he wrote a letter to our school about bullying and school harrassment that our school posted and the school strictly enforces anti bullying rules with no tolerance.It became a landmark case about harrassment.
In the human race, there is 2 sexes, male and female. They were meant to seek each other for procreation, through the enticing activity we call sex. That is the goal of nature. Anything else is the imperfection of nature, anomalies.Human beings can chose to be homosexual of are driven into homosexualism by internal hormonal unbalances, exposure to substances that can be influencial ( feminizing and masculinizing agents all around us that can alter a baby from its earlier stages in the womb untill later in childhood) and even enviromantal factors like the case at school I mentioned earlier. The fact that we respect others with those alternative lifestyles does not and can not erase the fact that homosexualism is not natural.
Any person getting offended by this reality should be objective and understand that realizing heterosexuality is the way the human race was made to perform in order to achieve natures goal, procreation and survival of the species.That is not the equivalent to say gay people are bad. Gay people are alive and we have to embrace them, but that act of acceptance and coexistence does not include shying away from reality. If the human race were intended to have homosexual relations as a norm, we would had been a hermaphrodite species.