I do think a person's job is a used does play a huge role on how others judge them. What is one of the first things people want to know about? What do you do for a living. The did a study where they had people rate male faces for attractiveness with no information given then had them rated with false job titles attached and their attractiveness shifted depending upon the desirability of the job.

I believe class is another factor in why Americans have a harsher view of people saying a job is beneath them. Americans have dim view of class systems and people who think they are somehow inherently better then because of their station in life. How much the sort of family you come from determine if you go to a university? Americans typically do not take kindly to statements seen as derogatory to people who earn a living the hard way.

Yes our history of with race doens't really fit that attitude but I think that is changing as well.