Having worked in retail I honestly cannot imagine a boss being so clueless, but I can believe these people exist, and not just in Japan.
The only thing that peeves me off, is the Japanese-mentality that "you gotta apologize and bend down no matter what". The good thing about part-time jobs, is that there's no reason to fight for your luxurious career at Walmart. But I get the feeling that we wouldn't be getting any of that in a manga.