There always seems to be an inclination toward biological determinism in drawing broad conclusions. It goes to the bio-psycho-social scenario: where the determining factor must be selected as one of the three, instead of a combination and interaction.
Especially in matters related to the mind - and therefore, also, the brain - the tendency is to assume a biological cause. Whether the issue is sexuality, "mental illness," or personality, a great deal of scientific studies (especially the ones that are popularized in the media) tend to be geared toward finding a biological cause of these human traits, often neglecting or dismissing social and environmental factors.
Take the brain scans. Do they really prove anything? Well, to me, they prove that there is different activity taking place in the different brains... which were studied. But the labels for the scans were, "heterosexual male," "heterosexual female," and "homosexual male." Have we determined what a "normal" hetero/homo brain looks like? What does a "normal" brain look like in general? Since we see different activity, is it precisely 'sexuality' that determines the change? If it is, do we know that it was the biological change that preceded the apparent change in sexuality, or is it the other way around? Obviously, the brain scan wasn't of the "suddenly-after-stroke-gay" man, so we have no 'before' and 'after' photos. He may just have used the stroke as an opt-out, not unheard of, especially in near-death experiences: almost die, decide to finally live life, be honest with who you are, discover who you are, etc. Maybe he's just pulling a Virgin Mary ("God did it!"). I don't know, you don't know, does the doctor somehow magically know the guy isn't lying? People are complex. Any gay man who spent a good deal of time in the closet knows how possible it is to live a lie.
I don't have the answers, but I also don't believe they are so simple. The doctor on the TV show said that this is a piece of evidence which proves that sexuality is biological. That just seems quite a leap to me. I have a lot more questions. Some things simply can't be reduced to being understood through a laboratory, a test, or an experiment. Alternatively, not everything can be reduced to mere environmental or social causes, the nature of biology must be taken into account. But with philosophers and social scientists staying away from science, and with scientists staying away from being philosophers (always rare exceptions!), I doubt we will advance too far on the path of knowledge and understanding, and instead, as we typically do, traverse the path of classifying, labeling, isolating, "perfecting," and thus, controlling. Throughout human history, the path of 'discovery' has often been a violent, dominating, and dehumanizing process.
Compared to other socially transformative phenomena and powerful institutions of human society (religion, the state, education, language, etc.), the realm of "modern science" is still relatively new to the human experience. Often, it still seems as if we are learning to use fire for the first time... and then burning down the house. The path of discovery becomes socially directed and organized, often without the knowledge of the scientists themselves, who are somewhat segregated and compartmentalized ("professionalized"). Modern science went through a particularly dark phase in the eugenics period, along with medicine, psychology, psychiatry, anthropology, sociology, etc., where "discovery" had an agenda: to classify and control.
Since then, the science has gotten better, just as all the various fields involved heavily in the eugenics movement have become more influential, more institutionalized, professionalized, and profit-oriented. They have advanced, but without properly reconciling with their dark histories, geared toward social control and domination. So while the methods have changed, the social direction still remains, though it, too, is advanced.
A little largely forgotten fact of history is that of the role of philanthropic foundations in shaping the modern society, namely, the Rockefeller, Carnegie, and Ford Foundations (among others). They were the financiers of the eugenics movement, the financiers and directors of the social sciences (developing and shaping entire disciplines), they funded psychiatry, psycho-biology, medicine, a Rockefeller Foundation official actually created the term "micro-biology" to describe a new field, leading to genetics, financed by the same names. It's challenging to find an aspect of society which philanthropic foundations have not been influential in shaping and engineering. These people are, and have always been, long term social planners. The aim is simple: control. The methods are varied and voluminous.