Dear me, such nonsense! (hardly surprising from the likes of STFC, a bit more so from Lord Cam)
Of course the man was being racist, ffs.
When the comments were made re the tories, they referred to a specific and very small number of explicit individuals. The likes of Collins and Daniels, not a wider cross-section of people. If it helps, I'm happy to say I'm a 'collinsist' or whatever the appropriate word would be. He can fuck off, and I still wish he would.
In this case tho, it is totally different. Blokey was asked about a wide group of people - people who have (arguably) good reason to fear a BJ mayoralcy. A more correct response would be along the lines of 'I think it is a great shame people view Boris in that way, he is certainly no racist and I am sure they will see from his actions that they have nothing to fear from him being the Mayor.' Instead he said 'fuck them.' That gives a clear view about his attitude to those people, to black people.