I have served in the military and I have been to Afghanistan. While numerous Afghans have traits like red hair or even freckles, they are the minority, and Afghanistan is at the cross roads of central Asia conquered by numerous countries and races. Hence nothing about that is unusual but they are not white and neither are most Persians.
1. Afghanistan is not in Europe, nor are they on a whole of European descent or even near majority of European descent. In short, Afghans would not pass the obvious visual test for being a European Caucasian. While being from outside of Europe doesn't ensure one is not white (ie. whites in South Africa are whites as are whites who have european ancestry in other parts of the world.) Even Afghans who possess common European traits like blue eyes or red hair are visibly very different looking. No one is going to mistake Hammid Karzai for being anglo saxon.
2. 50% of Afghanistan or about 14 million Afghans are Persians. Persians are basically elite Afghans (Pashtos - who are also present in Pakistan) who came to Iran to be in the centre of the middle east and have access to the Persian gulf. Iran is about 35% Persian and almost all Iranians in the West are Persians and not Azeris who are the majority and also non whites. No one would mistake nor consider neither Pakis nor Afghanis to be whites in fact almost all Pakis considered themselves part of the brown race like Indians and Bangladesh. So it is unclear why once they cross over into Iran they'd become white.
3. Iran is a fundamentally central asian country surrounded by Central Asians nations. The closest to white people in all of Iran are Azeris. Google Ayatollah Kohmeni, the grand ayatollah of Iran, and you will see why it is simply not possible than any of these people are white. Iraq, Turkey, Afghans, Pakis, Turkmenistan, Azerbajans, none considered to be white. No European person would consider even for a second a turk anything less than a muslim, and definetly not white (unlike white muslims in former yugoslavia).