dot: let us not be snookered by the language of "oppressor."
yes, or by the language of identity. in this case, "is".
"is" someone an oppressor? all the time, some of the time, in certain situations, with certain people, in what ways can someone oppress, in particular roles or relationships (for example, only when in "the shop"), with or without institutional authority, and so on.
to say someone "is" or "isn't" something implies a lot without much thought....or context....or relationship....or in this question, even a particular person or situation, just a generic (ahhh, the joys of economic systems) shop worker.