"Plain folks" is a form of propaganda and a logical fallacy.
[1] A plain folks argument is one in which the speaker presents themselves as an average Joe — a common person who can understand and empathize with a listener's concerns.
The most important part of this appeal is the speaker's portrayal of themselves as someone who has had a similar experience to the listener and knows why they may be skeptical or cautious about accepting the speaker's point of view.
In this way, the speaker gives the audience a sense of trust and comfort, believing that the speaker and the audience share common goals and that they thus should agree with the speaker.
This linguistics article is a stub.