Not just politicians Dave, but the "great British public" in general and all those pressure groups spouting BS just for their own ends, whether rooted in fact or just misguided "enthusiasm".
But we are all the 'great British public'. We are all subject to the same opportunities to find out the 'facts'. We all equally suffer from confirmation bias and so only tend to positively weight material which supports our views.
All we can do is to try to expose ourselves to as much contra-indicatory material* as we can to head off the effects or to stick to truly independent peer-reviewed science which always references its sources.
*Which is bloody difficult at times. Have you tried wading through the insane bollocks spouted by some of the loonier fringe?
