Richard Dawkins is all about promoting empirical evidence, science and the pursuit of truth. That in fact was his job, to communicate modern science to the public.
He isn't promoting a personal vicious onslaught onto believers, in context he is promoting the idea of openly discussing and ridiculing silly beliefs as currently they have 'special protection' in custom and culture in most on the world.
It wouldn't be considered offensive to question and ridicule someone that wanted to be president of the USA whilst believing in unicorns or UFO's, yet Romney literally believed in magical underwear and it was considered rude to bring it up!
Bush and Blair admitted to seeking advice in prayer, whilst leading the nations in war. This should be up for debate, discussion and ridicule! If Blair or bush claimed to be seeking the advice of Thor, ....... Well you can imagine!