However, sometimes I worry that you actually believe that someone from a middle-class background cannot be left-wing, and almost imply that you'd rather they be on the right..
I wouldn't say he does. Besides, some of Labour's greatest have came from middle class backgrounds. Michael Foot's father was a solicitor, he went to an independent school and was president of the Oxford Union. A similar path followed by many prominent politicians of all parties. I don't think anyone would, even without realising, wish to detract from great politicians simply because they didn't have the 'right' start in life.
As someone who went through the private school system at great financial burden to my parents (And, trying to refrain from violin music, were from working class ex mining stock who are now are pretty comfortable because of the opportunities they created for themselves) I was treated pretty nastily, in retrospect by some my working class (and yes adult) neighbours and friends and then embarassed by some of the 'monied' pupils at school. I was never quite comfortable in ether setting and I've always been irked by the use of class to deny or to grant access to anything. A narrowminded and misplaced 'working class pride' can be as damaging and as limiting as middle class elitism.