This talk,""Fulfiling Our Prophetic Mission,"  by Bishop James Conley, of Lincoln, Nebraska, is one of the best talks on equal dignity that  I've ever seen. 

Money quote:

We’re all sinners. We’re all called to holiness. But our dignity doesn’t depend on achieving it. God wills salvation for us, and we try to follow after him. When we acknowledge our common sinfulness and our common call to holiness, it becomes easier to see one another, not as objects, but as brothers and sisters in need of support, and encouragement, and solidarity with one another. When we are in solidarity with the vulnerable, the culture of life becomes familiar, and essential.

My mother, who spent a long time working in religious education for mentally handicapped children, made exactly the same point about not de-humanizing the mentally handicapped by treating them as "angels."  They don't need to be angels to matter--they need to be human--just like the rest of us.