Bodyworlds isn't disrespectful because the bodies were donated specifically for that purpose. Now, if they'd been used against their will, or their relatives' will, then it would be disrespectful (as I'd heard has been done with knockoff exhibits)...
After all, we cut up dead bodies and store them in pieces, or keep them preserved to see how all the parts work together, so we can learn anatomy off them; that isn't considered disrespectful because the donors wanted us to do it, because they knew we were going to be nurses and doctors and other professionals and needed to learn. There's absolutely nothing disrespectful about that. So why is it disrespectful if a person wills his body to art rather than medicine?
What I do think is disrespectful: Displaying Egyptian mummies, and other such ancient preserved bodies, in museums. Their relatives wanted them buried, not put on display. Somehow, the intervening thousands of years seem to have convinced people that this is okay... Personally, I would have them examined via x-ray and other non-destructive imaging, the information stored, and the mummies put back into their tombs where they belong.