Well I personnally don't think there is anything wrong with generalising or steriotyping, so long as you realise that they are generalisations and steriotypes.

Yes, Gauls were generally big, strong and emotional, but that doesn't mean they all were. Yes, Germans were huge, red or blond haired and truly terrifying in war but I'm sure somewhere there was a German who just wanted to stay home and compose epic verse.

As to Black Athena, there's a very funny bit in one of my Lecturer's book (Tim Whitmarsh, Introduction to Greek Literature) where he basically refuses to discuss it. That said the idea that the "Arian" theory was fuelled by racism may have some validity. Of course that doesn't make it wrong and it basically isn't.