I dont think the illness of dementia is remotely funny, but the behaviour it can cause some suffers to do are quite funny, more so when you see their "old" self.
I laughed at something the other day and it was not remotely funny, but it did/does have the comic/sketch book comedy that you only read/see in sketches.
I was actually ashamed I laughed at it when I came off the phone, so not sure if it was a nervous giggle or not.
Its was a man whose wife pulled him out of his wheelchair and started beating him up with his own prosthetic leg. I thought he was brave, because not many men come forward with DV, in what I do.
I then went into professional mode, done all the legal and seriousness requirements to protect him.
But afterwards I giggled, because the whole thing situation was just so bloody surreal.