Let's examine this statement. "Hispanic" means "of Spanish descent." And Spain is part of Europe. So how did people of Spanish descent get to be "thriving in California and the Southwest centuries before Europeans set foot in America"? There is a little deficit in logic here. Now if the author means that Indian people were thriving here long before Europeans showed up, I can agree, but he doesn't identify himself as an Indian, only as Hispanic.
Last year, I went to the Tamale Festival in Indio, Ca and was surprised to see lots of T Shirts for sale that said “I am not Hispanic, I am Mexican”. I always thought “Hispanic” was the PC term. It made me smile.