I think they were making a point about public space
Don't get me wrong. CMers aren't intellectuals. They simply have a visceral objection to the way space, particularly public space, is ordered. Riding en masse around the centre of London turns the street from something on the way from A to B in to theatre. People, tourists, commuters, revellers stop and applaud (the same thing happens to the night rides I organise).
The Olympics is about the privatisation of public space, whether it be a bit of the footpath in Park Lane, the Zil lanes or the Olympic Park itself. Put simply you and I can go to less places in London than in past times. That shouldn't go unremarked.