No food is inherently bad. If you eat one piece of candy a month, it’s not going to do anything terrible to your body. If you eat one Twinkie each year, it is not going to kill you. “Bad” is still a moral judgement. You can say some foods are more or less processed. But saying that some foods are “good” and some are “bad” is just an arbitrary moral judgement.
There isn’t really any “if,” we should be educating everybody about nutrition. But we also shouldn’t shame people for choosing to have a slice of american cheese or whatever.