The US Supreme Court on Friday ruled that same-sex marriage is legal under the US Constitution. The ruling is a major victory for same-sex couples, gay individuals, gay rights organisations and straight allies - those who are straight but support LGBT equality.

But it should also come as a triumph for those whose conscience appeals to reason and the equal right to life and liberty of all human beings.

In a global society where scientific advance, secular education and social mobility have redefined age-old theories of how we look at the world, the ruling is certainly the correct one.

What is significant about human advancement from the Dark Ages to the present? Simply that we now know more about ourselves and the universe around us than we ever have at any point in history. In context, we know that homosexuality is not a mental illness, and is not exclusive to human beings.

Some species of animals practice homosexuality with gay abandon. Concurrent with this knowledge is the fact that some species practice sex not just for procreation but also for recreation. Thus there is neither any moral turpitude in human recreational heterosexual activity nor in homosexual activity. It cannot be tied anymore to the creation of progeny.

Is there moral deviance? For ages, notions of accepted sexual behaviour have somehow been intertwined with the righteousness of heterosexuality. But because we have scientific proof that homosexuality is not unnatural, we must also reconsider these norms of accepted sexual behaviour. The idea that the way heterosexuals - or indeed any given individual - thinks about sex is the only correct way has to be debunked. Sometimes, the homosexual experience of a loving relationship may vary and even be at odds with the personal and social experiences of relationships between heterosexuals. This cannot be regarded as morally abhorrent. We have no reason to force LGBT individuals to accept and practice any particular causative and correlative relationship between love and sex. In other words, it is not maintainable to demand to know why 'homosexuals only think of sex'. (Not that this is a valid proposition anyway).

In countries where religion forms the basis of law, it is difficult to propagate even a scientifically-backed belief in equal rights for LGBT individuals. The path forward may involve developing a complex mix of enabling factors that are tied to the satisfaction of basic needs as well as the material prosperity of the inhabitants of the country. Then there is the question of convincing the society that their religion's stance on some issues may be scientifically disproved, or even morally unfit or contradictory in the 21st century.

But in countries where separation of religion and state is written into constitutional law, there is an even greater moral exigency to accept same-sex relationships (and marriage).

Let us take the 'religious freedom' argument against same-sex marriage - that it impinges upon religious freedom of believers. It is hard to understand this - how does another person's choice impact your religious beliefs?

On Friday, several pastors and conservative legislators said they feared the US Supreme Court decision would impede the practice of religious freedoms, though conservatives could continue to personally believe in the traditional definition of marriage. For example, the ruling may make it impossible to deny dormitories to same-sex couples in educational institutions. There is a strong sense of dis-empowerment among conservatives here, a fear that you can no longer 'live out' your faith.

Let me flip that argument. By opposing same-sex marriage on grounds of religious freedom, you are telling gay people that they can believe in homosexual marriage, but never practice it. However, in a secular democracy, the will of the people and constitutional machinery must stand superior to the will of religion.

In a secular democracy, no religious institution should have the right to deny people guaranteed civil liberties because of their sexuality. For example, you should never be thrown out of school or employment because you married a person of the same gender. The local hospital cannot deny you treatment because it is run by a religious trust and you happen to be homosexual. This is not religious freedom - it is the freedom to impose your religion on others.

The best that can be done is to allow priests who are opposed to same-sex marriage to refrain from solemnising them. In a secular state, religion cannot inform the public morality. Those who put forth the religious freedom argument hold the unfortunate belief that religion deserves special, superior consideration to any other belief system - and hence its mandate is curtailed by the appearance of something like gay married couples.

Here's an example of the absurdity of preferring religious doctrine over the laws of a modern secular democracy. Given the variety of interpretations of all religious scriptures and the proclivity of medieval doctrines to make claims that offend scientific reason, it might then be reasonable to argue, for example, that child marriages must not be prohibited by law - because they carry sanction in a particular religious text - and banning them would impinge upon the religious freedom of those who practice child marriage. Clearly this is not an acceptable moral position.

It must not be forgotten also that the religious freedom argument has been suitably used to uphold evils such as slavery, sexism and racial segregation in the past (and caste-based discrimination in the Indian context). Slavery today stands abolished in the Western world and racial prejudice is at least morally indefensible. Equal rights for women are at least written in the law. Could a similar path be followed in the case of the gay rights movement?

The other argument thrown in by opponents of same-sex marriage is that if homosexuality becomes morally acceptable, a day would arise when we would say the same of bestiality. This argument is severely flawed, for a simple reason.

Consent is the defining factor of any shared action between two living beings. Sex with animals runs contrary to the ideal of consent. No known animal possesses intelligence equivalent to that of an adult human being. Again, science informs us that the intelligence of an adult dog for example, is equivalent to that of a toddler. A toddler is not competent to understand sexual acts (and thus give her consent) and hence paedophilia is both illegal and immoral. Similarly, an animal cannot fathom human sexual activity and therefore, bestiality should be both illegal and immoral.

The one appreciable area of concern about same-sex marriages may be the ethics of allowing same-sex couples to raise children. The underlying philosophy against this says that the presence of two parents of opposing genders is essential for the psycho-social development of a child. There has been scientific research into this issue as well, and the results seem to indicate that having parents of opposite sexes is not necessary for the development of a child. But in this case, it is at least possible to empathise with the moral conundrum - because the rights of children are even more inalienable than those of adults.

But would acceptance of same-sex marriage promote social anarchy, general moral decadence and eventual loss of social fabric? I would argue not. Firstly, conventional wisdom suggests that any human activity might be acceptable as long as it does not inflict harm upon others. Second, societies have undergone upheavals at every stage of reform - whether it was the questioning of Church doctrine, abolition of slavery, women's emancipation or the movements against racial inequality. These changes have not brought about the downfall of civilization. Instead, they have led to a rational pursuit of happiness and greater well-being.

Finally, I would argue that a decadent society which upholds the right to liberty of every human being, is far more moral than a society which thrives due to everlasting oppression of huge sections of its own people - women, homosexuals, children, atheists, apostates and so on. It is infinitely more desirable to ensure human well being in all endeavours than to suppress it for the sake of some religious or tribal doctrine.