It does not make evolutionary sense for some one to want to transition. It makes them infertile and thus it should be selected out. This feeling of a need to transition is either the result of hormonal imbalance (too much or too little testosterone/estrogen) or the result of abuse or other trauma. All trans people I have encountered have pretty messed up lives so this would point towards the second option being more normal. While this may be an illness, It is currently uncurable so as to how we treat people with it is up to us to decide
I've always been against people encouraging those with gender dysphoria to transition to the sex desired instead of getting help for their mental illness because these people have a horrible mental illness that affects their lives and so we should not be encouraging them to go through with what their mental illness wants them to do. I liken Gender Dysphoria to other mental illnesses like depression and bipolar disorder, For people who have those mental illnesses, Their brain tells them things that are not true/it influences their lives in negative ways and they thus get treatment. But why are we not more concerned about getting people who want to mutilate their own genitalia the help they so desperately need, And instead let their mental illness rule their lives.
Sorry dude, It's never been a mental illness and hasn't been a disorder since 2013. So technically, They're completely sound of mind, And as such, Have every right to do whatever they want with their bodies. And of course, The only effective treatment is transitioning, Not a psychologist, Because it's not a mental illness or disorder.
Gender dysphoria is a mental illness, True, But so is anxiety and depression. We don't stop depressed people getting help because they "aren't sound of mind". Just because you have an illness, Doesnt mean you can't make decisions. People with gender dysphoria can make their own decisions about their body, And transitioning is often the only thing that can treat it.
Not transitioning can trigger depression, Anxiety. Why would we force somebody to go through those horrible things? Why can't we let them be themselves?