Family doesn't believe dementia diagnosis

My family is skeptical of my husband's dementia diagnosis. We have two doctors confirming it, but because he is not so far advanced that he is forgetting what year it is, or walking outside with no pants, many people in the family are resistant to hearing that my husband is terminally ill with vascular dementia. This has gone so far as one family member convincing my husband that I am "out to take everything away from" my husband. This family member visits MAYBE twice a year, but somehow he thinks he knows more about my husband's condition than I do..... And I've been the one to take my husband to ever Dr appointment since his strokes two years ago!

This family member's behavior has led my son to nickname his uncle "Captain Douchebag."

Other family members - again those who don't happen to live in the house and don't observe my husband's daily behaviors - have told me that I am blowing things out of proportion, and that I can't blame everything on the dementia. OK that last bit is true, but nowhere near as true as they think it is.... they think that if my husband yells "FUCK YOU!" at my 23 year old son (who lives with us) that my son must have done something to deserve it...

I know that there are others who struggle with this. Does anyone have any ideas for how to get the family members who don't live with the day to day reality of mid stage dementia to understand what kind of stress the family caregivers go through on a daily basis?