This is an insidious, inescapable side effect of the mainstream authors declaring that people they label "hoarders" are mentally ill.
This has the side effect of making any reasoning coming from people concerned subject to summary dismissal, to being ignored.
This really cuts any chances of meaningful, constructive, mutually respectful engagement to nil.
Just like with nagging and yelling, I'm going to suggest that this didn't get caused by or start with or is limited to the subject of possessions, nor does it end after hypothetical discarding of possessions.
A Keeper can have perfectly valid concerns, or the most insightful observation in the universe, and it will be dismissed - "What are you talking about ? Just look at the mess !"
It's hard to accept any arguments from a person who you believe is mentally ill / lacking insight ( as "experts" claim ), and who disagrees with you.
Treat a competent person as an idiot, you get an idiot.
This is the harm that comes from "mental illness" / "diminished competency" framing by the "experts". Everything else being equal, if we can do without those, we should - by treating the person with full respect and dignity, and as no less than equal in competency, and listening to each and every one of their concerns at full face value.
As it is, the Frustrated Family Members adopted the "mental illness" / "diminished competency" framing and ran with it, accepting it as the diagnosis ( "Aha! This is what you have!" ) without a proper analysis of the situation, without proper qualifications ( which even practitioners lack, given the existing mainstream framework ), without being impartial, and without any ethical considerations of what effect this has.
Or, I'll put it in simpler, layman terms -
Establishing a constructive, mutually considerate understanding when it comes to unconventional activities or possessions may be hard enough as it is, even under the best circumstances.
But, if
1) your spouse has been at their wits' end trying to convince or compel you to abandon your possessions / projects,
-AND-
2) they just found, from a book or a talking head on a screen, that it turns out you have this "mental illness" that is also "compulsive", that you're not quite in control of your mental facilities..
Q:
What does this do the prospects of the above mentioned constructive dialogue, and your ability to reason about your needs and to be heard ?
Check and mate, you lose.
From the standpoint of the spouse - it's exactly like going into a psychiatric ward, listening to the ramblings of an inpatient ( a friend, a relative ), and accepting those ramblings at face value. Do you see this happening ?
And, in a further twist, while having a person considered "mentally ill" might call for some gentler and more compassionate treatment, this doesn't stop some spouses from holding the person responsible like any competent person, when making demands and accusations, and nagging and yelling ( which is abuse ). Abuse of a person they themselves consider mentally ill, how do you like that..
Thus, the "hoarding" "experts" may have been to some degree responsible for destroying relationships and ruining lives, if not by causing this, then by contributing to the process and making it that much more inevitable and painful.
How do I know this to be plausible and known to happen ? I witnessed it firsthand, for one ; and it is an inescapable conclusion that this will happen again and again - the books from "experts", e.g. BIT, include parts addressed to "loved ones" ; and the chances that a frustrated family member will accept all recommendations, including ones to be gentle and patient, are not very high - the recommendations to be nice are the first ones to fly out the window as soon as tempers run high.
Hello Iatrogenic Harm - the "hoarding" "experts" fumbled with things they didn't fully understand ( or, in some cases, didn't understand at all ), and made it worse.
This is powered by a powerful "oversimplification engine" by people concerned - a very caveman-level "clean good.. garbage bad!".
I couldn't even tell the more benign and more closely related family members that actually there is a different way to think of it, and that the books from the "experts" they've read are full of, let's put it generously, errors.. who are they going to believe ?
They, who always came to dispense advice and opinions, even in their most gentle form, they who never even asked questions, they who never tried to understand, they who always kept trying to "help" by uninvited advice or uninvited action - will they suddenly admit "oh, it looks like I was wrong about this" ? Not likely, if I know anything, not without a massive change in the perception.
This is also why we can't count on this changing any time soon, this is why it may be counterproductive to even try to convince anyone at this stage.
Sad, that.