Ooooh, there was a proper set up for the conflict between Lutz and his family!
The anime really didn't do a good job at adapting that mini-arc.
@Fari Lutz's family is poor and see merchants as greedy money-grabbers who care for nothing but enriching themselves. Now they're seeing Lutz dressed up as and working as a proper merchant. Given they don't realize merchants need to give something in exchange for their work (goods that the population actually needs), they believe merchants are evil.
Ironically, though, seeing how the assistant at the shop the brother works at was the one trying to rip-off the little girl.
Goes to show how ignorance is not a bliss at all.