A few things:
- The video claims that genetics play a role in gayness, which may be partially true but doesn't tell the whole story. What is considered to be a greater factor is hormonal development inside the womb, which is mentioned later on. Fetuses that develop when the mother is stressed are more likely to be homosexual, something discovered during an analysis of babies that were in the womb during the London Blitz.
- ...they mention animals are often gay, but there's little mention of how birds are often gay, including (adorably enough) penguins. A current theory in ornithology is that birds "turn gay" as a result of a form of population control. When a population grows too large, some birds turn homosexual.
- The video really starts getting good at 2:41, where it talks about people that are "fixed." In the opinion of nearly every responsible and reputable psychological organization on the planet, homosexuality is a condition that is not curable. Science has a moral obligation to set the record straight and make people aware of this.
- Finally, I personally have always been of the opinion that too much is generally made, when explaining homosexuality, about biology instead of culture and definitions. Looking for a biological explanation for why people are gay as opposed to a sociological or psychological one always struck me as pointless, like looking for a biological explanation for something like politeness. What etiquette is differs from society to society, so how can there be an etiquette gene, anyway? Here's a dirty little secret about psychology: a lot of it can't be worked out from applied biochemistry because it's about the interaction of an individual and society. One of the greatest fallacies of modern times is that microphenomena can explain macro-level trends, and sometimes that's true (chemical structure determines properties at larger levels) but most of the time it isn't (crackpot explanations for how genes determine religious practices).