The human genome has only recently been mapped and we don't know what all the genes in a banana do. Also not all biological determinants are genetic. Chemicals introduced into the placenta can effect the development of the fetus. Maybe it was all those Malteasers my mother craved during pregnancy?

It's observed in nature and not just opportunistic sex (you find animals of the same gender pair bonding).

I certainly never chose to be homosexual.

It's very restrictive, most people aren't homosexual so the chances of meeting someone and clicking with them enough to get to know them and maybe enter into a relationship and marrying them are lowered drastically (especially when it's illegal).

Then there is all the name calling, the violence, the nonsense written on the internet and on the news etc

It would be a lot easier for me if I wasn't in this state so I doubt I would have chosen it as I'm by nature indolent most of the time.

Outside theocracies anyone following a religion chooses to and chooses to believe things without recourse to reason. That is not the same thing as finding yourself attracted to the same gender.

You don't have to believe anything to be homosexual you just have to fancy one section of the population over another.

It's no different from being attracted to people with ginger hair.

Calling any attraction to people with ginger hair stupid would be pretty stupid, especially it came from a book where the prejudice is attributed to a bronze age desert God.

See the distinction?