Brian, you are certainly entitled to your opinion, and while it is socially enlightened, it is scientifically incorrect.

'Race' is NOT a biological classification it is a political and social construction.
Sorry, but it is indeed a biological classification. This is not a matter of opinion, it is a matter of definition. Any good biology textbook can elaborate.

The notion of 'race' falsely assumes that humanity is divided into unchanging, natural types, that can be recognised by their physical features, which are transmitted 'through the blood'.
"Unchanging" is not part of the definition, and in fact is contrary to biological principle. "Physical characteristics" is more accurate than "physical features." Transmission is technically through the genes, often popularly referred to as "through the blood."

This false biological notion of race then allows for the ascribing of particular mental and moral characteristics to racial origin.
Take out "This false biological notion of race" (which is is a contradiction in terms) and substitute "Racism" ("racialism" in the UK?) and this would then be an accurate statement, as any good dictionary should confirm.

This, in turn, allows for the establishment of hierarchical classification systems based on apparent racial origins - i.e. the superiority of the 'white race'.

This has, of course, provided a useful justification for the exertion of imperial and colonial power and all that goes with that from slavery and apartheid to ethnic cleansing and genocide.
The above two sentences are examples of racism.

Viewed in this way it is possible to see that 'racism' is not the product of the concept of 'race', but the very reason for its existence.
The cart is before the horse here. The concept of race exists due to our system of classifying knowledge. Racism is the product of the dark side of human nature inappropriately applying race to areas where it does not belong.

To underline this point it is useful for people to realise that there is considerably more genetic variation within apparently black or white 'races', as between them.
I don't know about more, but certainly there are plenty of differences within races. By definition, race addresses only some characteristics. It is a somewhat arbitrary category, and your point here is well taken.

I applaud your and McGrath's disdain of racism, and I understand the feeling that there is no social merit to the concept of race. I just wish you didn't express this by denying that race exists as a biological category, because in fact it does exist. It may not be of much use to the average Joe, but it is useful to biologists. The fact that some misuse the concept of race does not negate its value in certain contexts, nor mean it is evil or wrong. One could just as well (and just as stupidly) base moral and character judgments on hair color or height or any other chosen physical characteristic. It's not the categorizing of physical characteristics that's the problem, but rather tying those characteristics in with other values. Race is inherently neutral and benign, racism is a scourge of humanity.