This always seems to be the same argument.
We are not trying to convert kids to anything. People are born the way they are born. If that's gay then ok. If it's straight then ok. Trans? Ok. At most, we just want resources to be available. A child shouldn't have to grow up being shamed and told they are evil just for existing.
The thousand of years argument isn't really valid either. There have always been LGBTQ+ people. Certain time periods just hushed everything, and/or killed us in some way. Do a little research.