I've said it LOTS of times - because I love our world being multicultural, and I'm sure positive nationalism (WITHOUT imperialism and conquest) is the best and most peaceful way forward for humanity.

This is an opinion and an assertion. It does NOT answer my question: WHY is it the best? Why is me singing a French song or a Frenchman singing an English song a handicap to the peace of humanity - eh? Quite the opposite, I would have thought - but then logical thought, backed up by external evidence, is not your forte, is it?

Evidence of the harmful effects of this cross-fertilisation, please - hard evidence.