I think I would write a letter explaining your husband's condition and put it through their door.
I think if you speak to them direct they will be embarrassed and do what most people do in that situation is get truculent awkward and difficult (or rather more so) and this could lead to a difficult confrontation. By sending a letter, they will see it and read it at home, without having to defend their behaviour.
I think most of us would like to string people like this up by their big toes, but they are neighbours and you have to live with them. So, give them the opportunity to suffer their humiliation in private.
You may not want to tell them what medical condition your DH has, but you could point out that a range of conditions can cause symptoms like those they saw: Posters on here have listed MS and diabetes and I would add epilepsy. I once went to the aid of someone with that illness when others were just assuming he was drunk. Add Parkinsons
Put the letter through the letterbox. Doo not expect a reply, but it should enable you to continue to be civil to this horrible family, even if between gritted teeth.