The problem is they believe in progress as the define it. They thing any as 'progressives' they have a monopoly on what progress is and where it goes. They assume any change or trend away from anything in the past is a good one and then they ignore the lessons of history that prove the wrong. They have some misguided faith that society evolves toward something and they think it is a good something. All the while they are dead set on believing that any smart thinking person who looks at the facts will come to the same viewpoint as them. And they they define 'facts' as what ever the media tells them.
Someone else said it on FR, but I don't know who or else I would give them credit for the statement:
The right bases its politics on morals, while the left bases its morals on politics.