How do you propose we disagree about it then
I’m nearing bedtime and can’t write extensively, but here are some starters:
Treat the person with respect. If your ideology tells you I am male, then fine. I can’t change that. But I do, on principle, react to being addressed as such, as it would hurt less if you beat me physically. If your ideology forbids you to address or speak of me in the feminine, then use neutral forms - “they”, “Rin”, even “the poster”. I will still notice, but I will be grateful that you made the effort to meet me halfway.
Make sure your analogies actually work. The problem with the eating disorder comparison is that not only are they drastically different in nature (eating disorders affect self-perception into believing things like you’re fatter than you are, while dysphoria comes from the actual state of the body), it is also a fact that letting an anorexic patient starve
will kill them, while in the case of severe gender dysphoria, sex reassignment has
demonstrable, significant positive effects. There is a reason why these therapies are still provided after more than fifty years of practice - they work.
I’m trailing off, but the thing about analogies that don’t quite fit is that they look tabloid, and not least are they often very patronizing or even offensive - like the perpetual “I think I’m Napoleon” nonsense. Thing is, there is no rational way to claim that someone’s brain somehow miraculously turned in to Napoleon’s brain, but there is an ever-increasing amount of scientific evidence which indicates that it is indeed possible for a brain to develop differently from the reproductive system. Transgenderism is a logically possible phenomenon, being Napoleon is not.
Further on, avoid the culture wars narrative. I have yet to encounter a transgender individual who wants to ruin everything that is good and holy, and it is offensive to be accused of such when all one wants to do is to be able to live a life without unbearable suffering. The culture wars narrative is a construct, a “them versus us” theme, which only causes hostility.
Additionally, try and put yourself in the other person’s shoes. It is impossible to truly understand gender dysphoria without having experienced it yourself, but at least try. Listen to the experiences of actual people. Try imagining how you would have felt in their situation. Try to remember that these people are actual people, and not some abstract, scary entity out to ruin society.
Lastly, be open. Consider whether the other person could have something to teach you; that does not have to mean the other person is right, but at least consider their arguments. I have had to adjust my views after being presented with scientific data which showed that my previous understanding was insufficient. It didn’t overthrow my position, but it nuanced it. However, I find that a lot of people, even after having had pointed out to them that they are misreading studies, or misunderstand what transgenderism actually is, still continue to present the same, fallacious ideas in the next (or even the same) thread. This is what makes misreading into misrepresentation, and a simple mistake into intellectual dishonesty. When I encounter this, I can only conclude that the person is not interested in any kind of real discourse, it’s like speaking to a wall. Given the fact that I have always adjusted my views when presented with more convincing data (this is how I ended up Catholic in the first place - I grew up Baptist), I find this to be perhaps one of the more frustrating parts, though it does not offend me - it’s just exasperating.
A second element in the above, is to consider whether the Church actually teaches what you’re brought to believe, or whether those of us who say there is no Magisterial teaching could be right. The document linked to a few posts back is not doctrinal, but pastoral. The conclusions people draw from it are also flawed - I have been over this more times than I can count, so I will not do yet another exegesis, but the short version is that it in no way makes any final judgement on the gender status of the patient (hint: transsexual surgery is not about “changing” someone’s gender, that is the tabloid version), and that it actually
permits surgical treatment where it is the only way to help the patient. Either way, it should be of concern to those who so heavily condemn sex reassignment, that the Church has never actually done so Herself.
Anyhow, I’m sure I could think of more, but at least these are some pointers.