That was the phrase that an off-blog acquaitance and sometimes visitor to this space used to describe those who deny the impact of human activity on global warming.
I love the passive wording of the description because it shifts the focus from the ignorance of the deniers to the cumulative result of their ignorance - "The sand is full of many heads" paints a vivid picture of those who choose to ignore the plain facts of reality without denigrating or condemning those who subscribe to this view. It's diplomatic but still accurate - this can be a difficult balance to achieve.
I would have just said, "they have their heads up their collective ass". But I have never been very diplomatic.
"The sand is full of many heads" applies to any number of situations where one side of an argument chooses to ignore the facts or chooses to have thier own reality - I plan on using it often and I have permission to do so. But I'll still be thinking, "they have their head up their ass".