Neurological studies show that these persons literally have the wrong brain for their physical gender, using surgery to modify the exterior is perfectly reasonable and for any reasoned mind would result in a physical change of gender. There's simply no argument against, you may have an opinion and that's okay but it doesn't mean that your opinion is of any value.
A problem we have, pretty much the world over, is a misunderstanding (for want of a better term) of the general public with psychological problems.
A massive majority of people have this idea that any psychological problem is something you can just snap out of. That OCD is just being fussy, being depressed is a choice, things like that. Things are getting better but it is very slow. We are only just getting through to people that being gay isn't a choice, and even that is a struggle.
It doesn't help that the terms are often misused, people are a bit down will say they are depressed, that's the worst IMHO.
I shall now get off my soap-box. Mental health issues is just a personal point with me, having been effected myself.