In fact, I am quite aware that mexico is a country with many flavors. And because I know that, I feel that I can say Mexican and drape the entire population with the "stereotypical mestizo" which you mentioned. Of course, even if I didn't, I'd still do the draping. But knowing about it just gives me a bit more security, knowing I have the experience.
But to answer your final question more precisely...
1. I don't care to be politically correct.
2. I have a sense of humor that can be very very horrible at times. Bear with me, I am working on it. 😀