She may be racist, but if in the course of her shopkeeping she sees that a much higher portion of kids from certain backgrounds break glasses, what is she to do? She's obviously seen more kids handle sunglasses than you or I ever will, and she can draw whatever conclusions she likes from that sample. She could have phrased her conclusions a little better though.

Of course she could just be a racist with a bias against minorities which she chooses to express through the medium of sunglass handling rules.