14,000 plus is an exceptionally large sample and it is nationally representative. The critical question is how discrimination is measured. The study authors add a very important caveat: 

"In turn, such a conceptualization on the part of respondents could be one reason for the preponderance of the other category as a perceived reason for the discrimination (or unfair) experience. If discrimination were operationalized in a different manner, one might expect a different pattern of findings. The “experiences of discrimination” (EOD) measure analyzed by Krieger and colleagues, for example, is a multi-item construct that has been shown to be a reliable and valid assessment of self-reported racial discrimination. Importantly, single item indicators of discrimination seem to perform poorly when compared to multi-item measures. As a result, we might have uncovered higher levels of self-reported discrimination if we had used a multi-item measure like the EOD."