I am born and raised in here the UK with ancestry from the UK, Ireland and Germany. I have only recently started to hear of Mediterranean people referred to as white, and assumed the opposite to above posters, who think Americans only tolerate Hitler's wet dreams as whites. I thought that this recent including of Mediterraneans as white was due to the American influence of calling everyone vaguely Caucasian white, due to less than half of US whites having more than 95% white ancestry. Legally, in the USA they even consider Arabs to be white. I certainly never thought of Spanish people as white or instinctively as "like me", unlike north or east European people from other countries. However we choose to label them with words, there is a visible difference between north and south Europeans.
They had a long history of being colonised and raided by Moors, as did other south west European countries, while the south-eastern countries of Europe where colonised for several centuries by Turks during the Ottoman empire. It is plainly obvious from looking at them that they have Arab/Turk ancestry. You only have to look at artworks from south European countries from before Islamic colonisation to see that the people there used to look the same as North Europeans. There is also the genetic differences between southern Europeans, and the fact they have more African DNA, which is almost non-existent in northern europe. Meanwhile in some northern parts of Spain that the Moors didn't manage to colonise, such as the Basque country, the people there still look like north Europeans. Its the same with north vs south Italy.
That is a very long way to say that I disagree with calling those who think that Spanish people are not white are stupid. It's a valid opinion based on the above facts. Most racial categories have subjective definitions and cut-off points, so who's to say one definition is more correct than the other? It's like the how many grains of sand does it take to become a "pile" philosophical question. We all know what a "pile of sand" looks like but at what point does it objectively become one? No one can say yet we all know what one is when we look at it.