Tom Sawyer said:
Because the two things are completely different and unrelated matters.
The only thing that people have against gay sex is not liking gay sex. There's nothing about it which makes it a negative in and of itself. Attitudes about it are entirely based on subjective opinions.
Mental illness, on the other hand, is a term with a definition and things either fit that definition or don't fit that definition. You can go on about homosexuality and breakfast cereals being mental illnesses all you want, but all you're doing is using words wrong.
No, I already showed repeatedly why you're wrong about that. I would recommend that you take a look at our exchange for more details on why you're wrong about that, but let me give a couple of reasons:
1. The concept of mental illness existed before there was any definition. In fact, people discussing what a useful operational definition would be already had the concept of mental illness - the intuitive, pre-definition concept.
So, what is the relevant difference between mental illness,
in the sense of "mental illness" used by people before they gave the definition, and immorality, objectivity wise?
2. The definition of mental illness is defined in terms of other, non-defined terms. In the case of whether homosexuality is a mental illness, well, it can be said that it does impair the ability to enjoy romantic relations with people of the opposite sex, or the ability not to feel sexually attracted to people the same sex, and so on.
Now, you say that singling one out is
inane, but "inane" is
not defined, and yet you agree, it seems, that there is objective inanity. Moreover, I would say that saying that gay sex is always immoral is
also inane, so why is it that homosexuality is not a mental illness, and that's an objective fact, but it's not an objective fact that gay sex is not always immoral?
What if the difference, objectivity-wise?
It surely isn't that some people gave a definition of "mental illness", for the reasons I've been explaining in several posts.
3. No definition of
illness has been given, and yet, there is an objective fact of the matter as to whether homosexuality is an illness, right? And there was an objective fact of the matter as to whether homosexuality was an illness 200 years ago, in the usual sense in which the word "illness" was used, which is the sense in which it's used now. Yet, no definition of "illness" is given. Or do you think that in order for there to be objective illness, a definition (i.e., an explicit definition) is required?
4. Generally, definitions are given in terms of other terms, and some of those are not defined, but used intuitively - or defined in terms of terms used intuitively, etc. If definitions were required for there to be objectivity, barring infinite definitional regress, there would be no objectivity of any issues. But there is no infinite definitional regress,
so there are objective issues in which the relevant terms are not defined.
So, again, why do you think this is a problem for objective immorality, but not a problem for objective illness, impairment, inanity, or for that matter horseness. There is no definition of a horse, right? I mean, dictionaries give definitions that try to approximate
a non-defined concept already in use
In short, the idea that a definition is required for objectivity is mistaken, and so is the assessment that the fact that some people (psychologists, etc.) gave a definition of "mental illness" makes a relevant difference that would justify your distinction between whether gay sex is immoral and whether homosexuality is a mental illness, objectivity-wise.