However, being on food stamps can be used as a measure of one's economic class, since in order to receive them, your family has to be at or below a certain income level.
Sure. But not receiving them is *not* a measure of one's economic class. Which was the precise point I was making. One could choose not to accept or apply for food stamps even if one qualified for them, right? So arguing that if someone wasn't on food stamps, they must not have been "pretty poor" is a completely false assumption.