I've always felt a slight inchoate resistance to them, but because I have my editing hat on this time I have to stop and ask myself why. I think part of the answer is that they're ambiguous. Do these phrases refer to the celebration of difference and diversity as such, or to the celebration of the individual cultures that comprise that diversity? This may seem like an overnice distinction, but I don't think it is (although neither is it an entirely clean one). As I walk down the Gloucester Road, for example, I may feel like celebrating the great Italian deli, the Vietnamese supermarket, the Polish cooked meat store, that Spanish place where they do a lovely Manchego, the Peruvian cafe and the local chippie. But do I celebrate them in sequence, giving due weight to each and the complex cultural histories that lie behind them - or do I celebrate the Gloucester Road as a job lot, for the fact of its diversity and the cultural history lying behind that? Of course, I can do both - but they seem rather different things, and when I'm asked to celebrate diversity I'm not sure which I'm primarily being invited to do.
Also, what form is the celebration meant to take? Should I buy party poppers?