I think the problem lies in the very heart of what it means to be conservative or liberal. Conservatives tend towards group-think because they’re either bullies, or the bullied. Liberals - by the very definition of the word - are a much more widely varied bunch that understand & respect other people’s right to have a difference of opinion. Therefore it’s much more difficult to achieve a unified front on the left than it is on the right. This is why the right dominates our lives so much despite being in a relative minority.