For the record, I am one of the Irish Gypsies, both by heritage and by choice, because I love to travel, something that most of my family had abandoned long ago, and I chose to revive.
I do not consider the term "Gypsy" as derogatory, but rather along the lines of "A Traveler", or one who loves to travel. In my terminology, gypsy, nomad, traveler, or fulltimer, etc. simply refer to those who love to travel, and prefer the great outdoors to motels or houses.
My family referred to themselves as gypsies, meaning that they left Ireland to travel to find a better place to live, traveling until they found it. My family then settled in the United States, and started a new life, putting down new roots. Parts of my family scattered the country, and my Grandfather took great pride in traveling the country to stay in touch with family, which I became a part of. We never stayed in motels, we camped in the woods, or by a river or lake, occasionally the desert. It wasn't a money thing, it was about enjoying and exploring the great land we live in. I was the only one in my family that chose to carry on this great tradition. I am proud to be a Gypsy, and there is nothing derogatory about it.
As in any facet of life, there are both the honest & dishonest people. In America we have groups of travelers who are of the dishonest variety. Many of them travel from town to town, selling home repairs then never complete the work. These same types tend to show up at flea markets, swap meets, and rallies. They are thieves by trade, and will steal you blind given half a chance.
I have had the displeasure of running into these types of people several times over the years, from the East coast, to the West, and North to South, they can be found most anywhere. They will impress you as average campers, the same type of people who normally you can trust. But they're different, they pack up and leave in the middle of the night, and take others belongings with them. What term is used to describe them is irrelevant, they are thieves plain and simple, and as travelers ourselves, and those who attend rallies, or stay in campgrounds, I think we have a greater probability of running into these undesirables and a simple heads up can't hurt.