Both

The masks show grinning faces, which lies to the people look them. 

But the blacks as a group of people often did not show the anger and the pain that they suffered. They disguised the anger to try to survive the harsh discriminative environment. They knew that themselves. This is what the poet tried to deliver.

see

• With torn and bleeding hearts we smile,

           And mouth with myriad subtleties.

• We smile, but, O great Christ, our cries

          To thee from tortured souls arise.