I think most of the points made so far are prefectly valid.
a) Yes, casting does have to be done (for the most part) with a large degree of specificity, and, in this respect, questions of what physique a person possesses, whether they are considered conventionally handsome/beautiful or otherwise, what accent they possess, what colour their hair and eyes are, whether they are essentially hairy or smooth skinned, young or elderly, able-bodied or disabled, whether they have a specific religious background, and so on are *all* called into play by casting directors, all of the time. In this respect, specifying 'race' (whatever that may mean in reality) - but, let's say, whether a character is white, black, asian, arabic etc. - is as justifiable as any other kind of specifiying. It *is* 'discriminatory', but only in the true sense of the word.
b) 'Racism' is itself a highly emotive term - to accuse an industry of being 'racist' is to suggest that it has an inherent and institutionalised need to actively belittle and abuse specific members of specific racial origins who work within the industry.
Tracey's points seem to me as valid a riposte to these claims as any other - what may have been true of the British acting industry in the 1970's, say, is clearly no longer the case. Colour-blind casting is frequently adopted by the leading practitioners of theatrical art within the industry (at the RSC on a regular basis, for instance). Many significant contributions are made to the industry by professionals who hail from non - WASP backgrounds, particularly in prime time television.
However, two additional points I will make:
1. What may be getting confused here is the issue of whether or not non-WASP actors are frequently 'stereotyped' within the industry. This seems to me to be a claim that (still, in 2008) has much more force to it than any notion that the industry is actually 'racist' in its casting policies. Thus, there remains a tendency to cast many Asian actors as doctors, or corner shop owners, many Irish actors as nannies or builders, many Jewish actors as accountants or taxi drivers, many black actors as hoodies or nurses etc. etc. These may be castings which relect, in some sense, the real demographics into which people from non WASP backgrounds fall in early 21st century Britain. But, at the same time, they are often castings which presume certain character traits applying to the role in question because of the character's origins. This can, I think, be a genuine cause of frustration to actors who have very specific 'ethnic' backgrounds the perception of which has been coloured by long - standing stereotyping. Though it may be equally true that many non 'ethnic' types find themselves encountering similar frustrations with casting if they belong to any bracket outside of the Home Counties RP speaker. How many times has someone Cornish been asked to play a fisherman, for example?
2. It is worth pointing out that there is always going to be a fundamental difference between the way stage plays can be cast and screen work can be cast, in respect to this issue. On stage, although colour blind casting has not historically been the norm, I think we will see ever more of it in the years to come - because everything on stage requires a certain suspension of disbelief in order to function. On screen, however, there is a powerful need to be seen to be 'accurate' in the depiction of the surrounding world (even in some of the most abstract pieces of work) because film is meant to approximate to visual 'truth' the majority of the times.
Therefore, if you are making a historically accurate adaptation of a Jane Austen novel for film, then there is very little opportunity for you to cast other than according to the basic criteria for the English middle classes of the era i.e. WASP. On stage, although it might be considered 'controversial' in certain circles (and, really, why should it be?), I don't see why you couldn't make a black Elizabeth Bennett work. The audience expectation is actually very different.
