Spiritually speaking, I do think the activity is a 'mental illness.' But, by activity, I mean 'all physical, sexual activities' regardless of (alleged) orientation. I say alleged, because my bias as a bisexual person feels that word is warranted. Perhaps a whole other debate. I reckon me writing words 'mental illness' in relation to 'all physical, sexual activities' is debatable enough. But, I don't think it is the type of 'mental illness' that is to be dealt with my mental health practitioners, nor do I see that having much chance for 'successful change.' I actually think such treatment would likely make things 'worse.' Would likely have people explore a whole lot of unnecessary paths, and ultimately would be about them (the practitioners) witnessing to an outer, or apparent, change to what I see as inner dilemma. The correction is not, even a little bit, sexual. I don't see one right way on this planet to be sexual. And the idea that we now have a plethora of sexual activity is, to me, a sign that our attempts at outer solutions are actually having opposite effect from what we intend. Such that if we intend to curtail rape by seeking outer solutions, I see that as inadvertently causing more rapes to occur.
When I say 'mental illness' I mean something close to delusion that thinks sexual activity brings about a) enjoyment, b) intimacy and/or c) greatest possible connection. Thus, marriage or not, I don't see how that would matter, other than societal attempt to control / limit the activity to as few people as possible. Given how over the top messed up marriage is on the planet, I really don't see how that is viable solution to whatever is seen as 'problem with sexual activity.'
To me, the solution is a) forgiveness and b) do 'this' instead. The first of these is to realize that whatever judgment 'we' appear to have about offensive sexual relations is entirely on each individual hanging onto those judgments as if they are fully righteous and God/nature agrees with them. The latter is spiritually loving (one and all) in way that does lead to a) actual joy, b) actual intimacy, c) greatest possible connection. I don't see that personally relying on physical mean to do this. But the kicker is that the physical is rather meaningless, thus if someone for at least the short term needs the delusion to help make that work for them, then really who is to judge that as (inherently) offensive? Which goes back to the (a) solution. Or judge not, lest ye be judged. Or put yet another way, it's not like your chosen path for sexual attraction/activity isn't plausibly a mental illness from the strictly spiritual perspective.
Would've been much easier to fit in to worldly understandings to not include the above 3 paragraphs in this post, but I'd rather have stated this than not. Above all else, I'm yet to see good reason why anyone ought to feel guilt over sexual attractions they have, and do see reason to resist that type of thinking at every turn. But also wish to be clear that promoting the activity as if that is necessary part of the attraction is where I see the problems consistently arising, both politically and spiritually. That's as true for heterosexuals as well as homosexuals. And yet, regardless of what I am implying, there's simply no way to stop the activity any time soon, nor should there be. No reason to advocate for guilt and good reason to advocate for forgiveness, as if there is another way to filter all of this.