I think that if you are experienced with it and have the setup to manage it, and also the know-how to recognize when a case is acute and with a defined cause vs. long-term with potential underlying issues, then it's a great thing to do to take on one of these horses. However, some horses are laminitic for complicated reasons - they might have Cushing's, they might be exceedingly sensitive to sugars in their diet (even in hay) and mineral balance, and even long-term laminitis with no rotation of the coffin bone can lead to serious hoof problems including bone damage. In many many cases it's just as simple as taking the horse off pasture and grain, but there are cases where it is much more difficult to manage and I would not blame anyone for not feeling comfortable taking on that unknown risk, especially in a boarding situation where you might not have control over the hay supply or be able to soak hay or control whether people might come through and feed random things to your horses. Not to mention the emotional toll it takes and for someone who just lost a horse in tragic circumstances, I would not blame them for not wanting to take on a known problem that can sometimes be a "black box" issue.
People selling horses can lie and they can also be ignorant. So they may say this is the first time the horse has had a problem, and they may say it's only gone on for a short time, but it's possible that the horse was subclinically laminitic for years before having a really bad episode and either no one noticed or they are lying about it. If you know what to look for you can often tell when this is the case but hoof X-rays would still be highly recommended, as well as an honest conversation with the horse's vet if you can, to get a real handle on how serious and long-term it is. But you still won't know the real truth until you get the horse into your hands and find out whether it really is just as simple as a proper diet and a good trim. In a lot of cases it is - but in some it isn't and those can be heartbreaking.
People selling horses can lie and they can also be ignorant. So they may say this is the first time the horse has had a problem, and they may say it's only gone on for a short time, but it's possible that the horse was subclinically laminitic for years before having a really bad episode and either no one noticed or they are lying about it. If you know what to look for you can often tell when this is the case but hoof X-rays would still be highly recommended, as well as an honest conversation with the horse's vet if you can, to get a real handle on how serious and long-term it is. But you still won't know the real truth until you get the horse into your hands and find out whether it really is just as simple as a proper diet and a good trim. In a lot of cases it is - but in some it isn't and those can be heartbreaking.