To defend this statement, I would look at some things that one culture thinks of as basic human rights but that other cultures do not.
For example, you could look at something so basic as the idea of the sanctity of human life. Here in the West, there is the idea that each human being's life is precious and must not be taken unless there is a very good reason. But then look at the attitudes of the cultures of other places and times. For example, we know that the medieval Japanese attitude towards life was much less respectful.
There are many other examples that you could point to, such as the example of women's rights. By looking at such examples, you can argue that human rights are not universal.
In 1947, the American Anthropological Association (AAA) wrote to the UN Commission on Human Rights to advise them on the forthcoming Universal Declaration of Human Rights. The AAA argued that, because individuals must exist within their cultures, to respect an individual is to respect their culture. Cultural relativists object to universal rights because they believe that moral claims are a product of one's culture and, therefore, should apply only within that culture. For example, many critics note that the Universal Declaration of Human Rights tends to articulate a "western" morality that focuses on individual, civil, and political rights. Cultural relativists point out that cultures with more robust community structures tend to value group rights much more than individual rights. A cultural relativist would argue that it is impossible to claim that one of these approaches is morally superior to the other and that it is arrogant (and maybe even imperialistic) to apply western conceptions of morality outside of the west.
On a more practical level, there is much disagreement (even within cultures) about what constitutes a “universal” right. Some scholars contend that human rights must bear a clear relationship to practicable duties. This essentially means that if something is impossible to achieve, it is absurd to claim it as a basic human right. For example, Article 24 of the Universal Declaration of Human Rights identifies the right to “periodic holidays with pay.” In reality, this right would be impossible for many governments to promote or protect. Even scholars who believe in universal rights have expressed fears that including too many “impractical” rights pushes all talk of universal rights into the theoretical realm. Their concern is that, if too many rights are “ideals” that cannot actually be accomplished, human rights treaties will be viewed merely as descriptions of some utopian dream rather than lists of real rights that governments are morally and legally compelled to enforce.
I agree with the opinion of pohnpei397. I would like to add a something. You could say that Human Rights have the "desire" of being universal...That's how they were thought to be, but in reality that's not absolutely true (for different reasons). One of the reasons were previously written by pohnpei397, but you also have to make a distintion between the classes of human rights (they are 3: but the traditionals are civil rights, and the social-economical and cultural rights). Authors say that the first category, is one which is more "easy" to acomplish (taking in account the cultural differences), the second one includes rights that even if they are "guarantee" for human beings there is process on their achivement, there is a base from which the state -who's the one who has the obligation to respect and make sure they are respected by other citizens- cannot go down...with and example it'll be clearer: health: if you have the right to get free flu medicine, the state cannot take it away, because that's the base, if they want to add more benefits better, because it helps to fullfil the human right.
If you undestand universality as something that is for the whole earth in the same conditions, human rights are not universal. If you study them in a specific community they aren't either. Theoretically they are universal, that was the spirit of the declaration. And the idea of the UN documents that follow the declaration was to work hard to arrive at that universality without losing the inner social differences.
There is a lot o material over the web and libraries that will help you. It's also interesting to read the origin of the declaration of human rights of the UN, because there you could read the different points of view of the universality between west and east.