More on this at
http://news.bbc.co.uk/1/hi/entertainment/tv_and_radio/2518151.stm including a still from the Bush-mocking animation in question.
Of course we can make fun of Bush on TV over here - if we couldn't, 'Have I Got News For You' would run about ten minutes shorter every week. However, this bunch of over-enthusiastic regulators seem to be applying the principle that people choose to watch satirical TV shows (and thus should expect humour some people might find offensive) but are exposed to TV ads more or less at random. This makes slightly more sense, but still not much.