This one hit almost every one of the series' weak points.
First, making fun of people instead of making a real argument is Title-of-Show. It doesn't prove anything and just makes you look desperate for material. The first guy's main sin was being too grumpy all the time, and writing a book about it, but I'll stab myself in the eye with a fork if Penn has never gotten pissed off by someone driving like a moron. We all get irritated by inconsiderate people from time to time; maybe a better angle would have been showing how pointless it is to get worked up over them.
Second, the manners teacher did seem to be charging a lot for her classes, and she was kind of a harpy, but she's not holding a gun to anyone's head to take her classes, or yelling at people at random in public for eating hamburgers the wrong way. If there are segments of society or social events that would expect those manners, what's wrong with someone teaching how to handle those situations? Will we see a show about how ballroom dancing class instructors are all fascists trying to tell everyone how to dance?
I tend to agree with P&T on shows where they go after people who are exploiting others, or harming people or society in some way. But this -- meh.
(Ironically, this site did not allow me to use the title of the show in my review, even though it's clearly visible above -- talk about manners!)