You are correct, and I am not dividing anyone.
When you go to school for cutting hair, some schools only teach you how to cut certain hair textures. Based on my experience, I don't think the barbers at supercuts are usually trained for cutting ethnic textured hair. Since the dude in the twitter post is black, mentioned black peoples hair.
In fact, now that I remember, when I went to supercut the lady that did my hair cut told me she never cut a "black" persons hair before. So I would assume they aren't trained for a diverse array of hair textures from people of different ethnic backgrounds.