This image 'as the title in the picture says' is about the purity of emotions people with Down Syndrome have. If they're happy, everything is wonderful and they are the happiest people in the world. But on the other side, when they're sad or angry, this will reflect on everything in their surrounding as well. If they're angry, than everything is bad.
You can see this as a negative thing, but i think in this case we need to be more like them, than they need to be like us. If they don't like someone, they won't be kind to this person. And when they like someone, they will let this person know as well. This pureness and being their true selves is someone we "people without down-syndrome" can learn from them. Cause when we don't like someone but we still need their help or something similar, we will pretend to like them and for example laugh to their jokes, even though in your head you don't find it funny at all. Being our true selves is something we can learn for people with down-syndrome.