One can only try to figure out what "causes" homosexuality. Some argue that homosexuality is genetic, others claim that it is a choice. This question will remain unanswered for a while (I am sure).

The fear of homosexuality, on the other hand, is societal and moral. Some people simply fail to accept it given its taboo nature. Others reject it based upon religious ideology. Essentially, people will have to give up one thought or another in order to find acceptance of homosexuality.

Scientists have done a fair amount of research into this topic.  Twin studies, starting with one in the '90s that showed that 52% of identical twin brothers with a gay brother were also gay vs. just 11% of non-twin brothers, show that sexual orientation has a significant basis in genetics.  

A recent Italian study found a relationship between a gene passed down from mothers to children on the X chromosome that promotes high fertility in mothers and their children, but is also associated with gay orientation. The study only looked at men, so we don't know yet whether that's true of gay women.

Environment, too, seems to play a role. Blanchard and Klassen (1997) were the first to produce a study on birth order, and their research found that maternal antibodies produced when a mother is pregnant with a son can affect the sexual orientation of her sons, with the chances of a gay son increasing by about 30% with the birth of each son.

I couldn't begin to guess why there is such animosity toward GLBTQ folks lingers in America and rages violently in countries like Iran and Uganda. Fortunately, however, it seems like young people are more inclined to take a 'live and let live' approach.  After many years of growing support among young people even as they age, recent polls show that support for gay marriage (one indicator of a supportive or neutral reaction to gays and lesbians) has reached a critical mass, and the majority of Americans support granting the same rights to gay couples as straight ones.

Homosexuality has a biological basis for some people, and for some people it's clearly a choice. With so many people being openly gay now, and with the gay community constantly in the forefront of political marches and grassroot movements, it seems like homosexuality is much more accepting in this country. But, I say that as a straight woman who doesn't have any personal experience with what gay people go through on a daily basis. I do think a lot of the shame and persecution has been removed. 

Perhaps the question has become: "Does it matter why a person is homosexual?" Will it change the person to know why he/she has the sexual orientation that he/she has? The answer for the gay/lesbian person is that it would make all the difference in the world if biology and homosexuality could be connected. 

Until a few years ago, sexual orientation used to be called sexual preference. The terms denote obvious differences: a preference is something that is chosen; an orientation is something that defines an individual.  What is the importance of the different phrases?  If homosexuality is not chosen, but actually is a biologically-determined characteristic with no choice involved, then laws should not treat gays and straights differently. Homosexuality, then, would be equivalent to one's race, over which we have no control.

One answer comes from a gay rights advocacy group that states:

'Proving people are born gay would give them wider social acceptance and better protection against discrimination.'

In other words, if a person is born with a problem, he cannot help it and should be treated accordingly. In the last decade, as this "biological" argument has gained momentum, polls have determined that Americans have become more accepting of and tolerant toward homosexuality.   

The Family Research Council, a conservative Christian think tank in Washington, D.C., does not believe that people are born gay:

"This would advance the idea that sexual orientation is an innate characteristic, like race; that homosexuals, like African-Americans, should be legally protected against 'discrimination;' and that disapproval of homosexuality should be as socially stigmatized as racism. However, it is not true."

Personally, I think religion and tradition are excuses people use.  People are always not going to like things they don’t understand.  We fear what we do not know.  As long as it is socially acceptable to discriminate against homosexuals, people will do it.  It is just like racism or sexism.  People will do it as long as they can get away with it.

The social reaction to homosexuality is, in my view, based on a number of things.  I would argue that the two most important are:

Religion.  Societies in which many people belong to very traditional religions tend to be much less tolerant of homosexuality.

Tradition.  In some societies, homosexuality has long been an accepted part of life.  This sort of tradition affects the way in which homosexual behavior is perceived.  This is similar to the ways in which some societies traditionally are more accepting of infidelity in marriages than others are.  This tradition can, of course, be affected by religion.