I've just had a look. The whole web site is trying (not very successfully) to take the rise out of all, and be satirical. Purile is more appropriate.
In my last job, I covered about 150,000 miles in three years - mostly on motorways, during which time I collected 9 speeding points for exceeding the national limits, so I'm not a slow driver by any means (although I now pay more attention to the little yellow money grabbers!) My car's on board computer, when I replaced it last year, tells me that my average speed during this time was only 45mph! This low average was due to all the motorway hold ups we constantly get. So to say that caravanners slow everybody down and cause hold ups is a myth.