Oh dear.
Would it be reasonable to assume that a lot of your sense of self is invested in how much you don't let the MS dictate your life and that you thought your DH was on the same page as not viewing the MS as something that disables you?
I can't imagine what it would have been like when you received your diagnoses or what the cultutral attitude to diabilities were at the time.
Neither do I know what you thought your future looked like at that time - back in the day, attitudes to such things were not enlightened and people with disabilities were looked upon as being 'less' than people without.
There was a stigma, no doubt about it.
Whilst even I am not naive enough to think that everyone has moved on from those dark days - time and attitudes for the majority have.
So someone referring to MS and by extension you, as a disability may not be a comment on who you are - just a nod to practical matters.
I don't know your private fears about how the MS will develop in older age , maybe this is triggering your reaction?
I don't know if any of this is applicable obvs and forgive me if I've overstepped.