The Human Person

Who decides what a human being is? And who decides that a human has intrinsic value (that is, value beyond the capacity to contribute to a particular society in a meaningful way)? Is a gay person human? How about a black person? A Jewish person? A communist? Most would offer a resounding "Yes." Most, I'll wager, would say that all these people groups are human and are valuable and contribute meaningfully to society, enrich society with their talents and ideas. But what about a person who cannot contribute meaningfully? What about a person so disabled that there is no hope of them contributing? What about a criminal who has endangerd the way of life for others? As one atheist colleague put it, if we can say that foetus isn't human then it's a simple matter of degree. So who is a human being? Does a human being have intrinsic value and why?