Does liking futanari porn or transgender women make you gay?

Mogu-sama said:
Good question, actually

We have to consider the two parts of the title "mental disorder"

We'll define disorder first, using the definition as applied to the medical world:
http://www.oed.com/view/Entry/54859
5. A disturbance of the bodily (or mental) functions; an ailment, disease. (Usually a weaker term than disease n., and not implying structural change.)

Then mental:
http://www.oed.com/view/Entry/116537
2. Carried on or performed by the mind; taking place in the mind; formed in the mind. See also mental arithmetic n., mental reservation n.

Therefore, a mental disorder is a disturbance (a kind block in function) to actions carried out in the mind. For example, processing information is an action carried out in the mind; we would call it a mental disorder when that condition impedes the processing of information and can be isolated as not being a symptom of a physical issue (for example, chronic pain)

But maybe that isn't good enough, psychologists use the DSMV (some of them, at least):

"The current version of the DSM characterizes a mental disorder as “a clinically significant behavioral or psychological syndrome or pattern that occurs in an individual [which] is associated with present distress...or disability...or with a significant increased risk of suffering." Here

There is a philosophical concern of whether we consider distress caused by social taboo to be clinically viable in a diagnosis. It's unlikely to be reasonable to assume that, as then anyone with opposing political concerns who has faced distress over that would have a mental disorder, which is inevitable on some issues if you speak of them

But we'll consider this in the case of homosexuality, bisexuality, and transgenderism, so:
"significant behavioral or psychological syndrome or pattern... associated with present distress"

Then we must consider the where the distress of an individual comes from, if you ask me and I'd hypothesize any other homosexual people, I'd say that it isn't homosexuality itself that causes any distress. Rather the social reaction to that status, how people perceive and react to you

Therefore -as we consider any sexuality to be a significant behavioral pattern- because homosexuality/bisexuality does not cause distress by itself, it is unreasonable to classify it as a mental disorder

Onto transgenderism, which is second-hand knowledge to me, but I think I can make a case. Undoubtedly transgender individuals experience distress, at least at some point, this sense of distress comes from two primary sources:
a) Social discrimination
b) A body in-congruent with their mind

We already discount social discrimination because that is not the condition itself, so we have to look at the gender dysphoria caused by B. Transgender people do not have an issue of self within their own heads, I'm rather sure they know who they are and only experience the dysphoria on account of their body not matching up. As evidenced by the elimination of gender dysphoria post-transition.

So, the GD comes from a physical component (the body) and is eliminated by physical actions (transition of the body). GD cannot (to my knowledge) be treated with any form of mind affecting drug (anti-depressants and the like).

Now consider how we categorize other disorders, say, a headache from dehydration. The distress (headache) is caused by a physical component (lack of water) and is treated with a physical action (consumption of water). We consider this a physical disorder

As such it is then reasonable to consider how we categorize transgenderism. The distress (GD) is caused by a physical component (body incongruency) and is treated with a physical action (transition of the body).

The DSMV specifies "a behavioral or psychological syndrome or pattern", yet in this case we cannot directly observe the mind as being the instigator for the distress. Rather that in all cases I am aware of, the issue is with the material and is promptly solved entirely in the material.

If I failed in my logic somewhere, do tell, I haven't puzzled this out so extensively before