This is terrible, Travie, so sorry to read that! No person ever has the right to laugh you off and if a dental care professional does that then they must have lost their mind! How unprofessional??!!
Dental care should be available for everyone regardless of any mental of physical health conditions and there are dentists who will be happy to treat you. I can‘t even imagine how discouraging your last experience must have been but please, keep on looking. There are kind caring dentists out there who will treat you with the respect and care you deserve, even if it might look difficult to find them.
We have a recommendation section here on the forum. It might be worthy to take a look if there is anyone in your area and contact them to ask whether they can help or tell you where to search.