I'm not sure I understand your question. Are you asking if you were discriminated against because the agent was Hispanic and you weren't? Or because you are Hispanic? Do you feel asking you to place your carry-on in the measuring frame is a discriminatory action? Is it possible the agent (TSA? Airline?) thought your carry-on was oversized and wanted to verify it?
I'm of Hispanic descent, live in Miami, and travel frequently through MIA. I haven't experienced any discrimination by INS or TSA employees at MIA, despite having gone through it literally hundreds of times throughout the years. Inconvenience, construction, bad food, high prices, rude or stupid employees, long walks from the gate to immigration, random rules and regulations, yes - overt discrimination, no. I've been discriminated more at the HDR.
mh