'All the main ideas of a sane man are irrational'

'All the main ideas of a sane man are irrational erections built up, for better or worse, to express his deepest feelings.' 

So says the wise Dr O'Grady in Andre Maurois's wonderful The Silence of Colonel Bramble. 

The doctor is right and this explains why perfectly intelligent people say such very stupid things in political discussions, particularly if they are liberals. People are not interested in evidence when they are expressing in a disguised way their deepest feelings. 

Of course this is true of conservatives too, but their ideas are common sense: at worse stupid or mean-spirited, rather than crazy.

The psychologist Robin Skinner says something similar, that all passionately held political positions are ways of dealing with psychological issues.