"So we are all biologically born heterosexual. No one is "born gay" because if they were born gay, why would gay men be born with sperm to inseminate a woman and get her pregnant?"

This is a typical religious understanding of biology. Evolution and biology has not been designed with a purpose in mind from some higher-being. Biology just is. That means nature is full or strange things which may seem contradictory.

So yes you can be born gay. That happens all over the animal kingdom. You think the animals have access to twitter or are exposed to gay activist groups? Of course not. That humans and animals on occassion get born gay is totally normal.

If you analyze the design of any animal including humans you will find a lot of design choices which make zero sense.

Does it make sense for people to be born blind? Why are they blind if they are born with eyes? How does that make sense?

No, it doesn't need to make sense to be true. Biology isn't perfect. None of us are perfect. We all come with our own flaws and problems. We get born with propensity to become alcoholics. Some of us are born with sever problems with controlling temprament. Others lack ability to concentrate. Some are born left-handed as opposed to right-handed.

It seems absurd to me that some people are going to pass judgement and say "You cannot be gay because that isn't natural!!"

That is like insisting people cannot be left-handed because the normal thing is to be right-handed.

Reality is that the most normal thing about being human is to not be normal. Each of us deviate from the norm in one way or the other. It is cruel to single out homosexuals and suggest they are more abnormal than the rest of us. We are all abnormal in our own unique ways.