I assure you, I am arguing in good faith.
I am not transgendered. I cannot claim to know what it feels like to be in their shoes. I don't know all the answers to why some people are transgendered and some are not. I don't know how one can be sure that one is transgendered or not.
I can tell you what it's like to know a few transgendered people, both young and old. I can tell you what it's like to see vitriol being thrown at people for being who just want to openly, and peacefully, live their lives as who they are. I can tell you what it's like to see that destroy a person. Nobody should have to go through that.
I'm not trying to win a discussion. I'm trying to provide a different perspective from a straight cis-man who, for nearly 20 years, has been welcomed into an LGBT community. These are good people. They deserve some respect.
(Yes, that is an appeal to emotion, but how else do you respond to an appeal to emotion?)