I agree that the word "Brit" isn't significant here.
It significant to Sky because he is their rider, not because he is British.
Having said that a few of the people who used the word "Brit" may have been using it, not as a racist generalization that since he is British that means British people are more likely to dope, but rather as a response to the idea that has been put forward in the past - that Brits and anglos don't or are less likely to dope- with the latest news on JTL representing to them evidence that reputes that theory, which brings out a truimphant - "I thought Brits didn't dope".