Why do middle class lefties believe stupid things?

The Telegraph's Ed West thinks he knows:

'I know many Left-wing people who don’t have a single conservative friend, and almost never hear a single conservative view expressed directly or on the radio, nor do they read a single dissenting opinion.

And so when I – a seemingly normal person (I hope) – suggest that, contrary to the assumed consensus, the EU is a stupid idea and opponents are not xenophobes, that most social studies do suggest marriage is pretty important for a child’s wellbeing, or – my nuclear option, and only if I never want to get invited back for dinner – Enoch Powell was right in his two 1968 speeches (and he never said “rivers of blood”, yer morons), it’s as if I’d just admitted to grooming children.'

As Winston Churchill, allegedly, put it: "Anyone who isn't a Liberal before the age of 30 has no heart .... and anyone who is still a Liberal after the age of 30 has no brain"