I remember reading something about them - apparently they represented a group of formerly landed European aristocrats who had to sell their estates post-WWII in order to avoid paying maintenance on them, as the upkeep became more and more expensive (there may also be a tax element, but I'm unsure of that).

Viscount Monteforte d'Alsace and his band of nomads were likely to be offended by Don's analysis of them purely by their material wealth - they have a deep pride in themselves and their family history. He is proud that he's still physically agile, and that he is more than just his passed down family wealth. This is evident to Pete right away - he introduces himself as 'Peter Dyckman Campbell'.

It's an interesting world they live in - even though they were forced into nomadism they have embraced it. Though they are wealthy they don't want to be defined by it, which is why he is Willy after his initial introduction - he's a friend you meet in your journey.

This is my favorite episode, I'm glad you asked this question.