There is nothing at all wrong with comparing the conditions of different groups of workers. To say otherwise would mean that much labor hsitory could not be written. EP Thompson distinguishes between craft workers and those who labored in the early mills. The craft workers were first to unionize, and his descriptions of their lives help tell us why and also give us insights into their politics. If I say that certain workers have greater control over their work, this is simply a matter of empirical reality, as long as I define what I mean by control. Now if I say as a worker who has greater control that I will do whatever I can to maintain control, no matter what it costs other workers, that is one thing. But if I put the issue of worker control squarely on the table politically, that is a different matter altogether. I used to say that everyone at the college should be paid the same; my labor was worth not a dime more than that of the custodians. This was never going to happen. So some of us worked to help the custodians unionize. Used our relative privilege to help make up for their lack of privilege. What is reactionary is for auto workers to badmouth teachers for striking and saying, as some of my UAW students did, that the teachers had it made because of all the time they had off in summer. Similary if public school teachers don't support cafeteria workers. We have a diverse and unequally situated working class. Solidarity is hard to achieve, and invidious comparisons are often made. Pointing out differences is not, however, invidious.