It does reinforce the average ideas in a group, but just because there is a group of people, and they are being marginalized in some context, doesn't mean the term "marginalized group" is appropriate. It means marginalized socially and economically, in a broad sense.

In the same way "hate speech" is short for "talking about hating people for their inherent qualities" and not "saying you hate kale"

The implications and logic wrapped up in that phrase don't apply to giving a PMC neoliberal downvotes when they post dumb shit here.