I always feel that the behaviour of travelers is a Catch-22 situation - they feel that are outsiders, unwanted and unloved by mainstream society, and as a result, they behave in a manner that ensures they will remain unwanted and unloved, and the situation perpetuates itself.
There is always a strong feeling of community in traveler groups, and they resent outsiders, regarding themselves as a separate enclave with no responsibility towards other people.
This attitude is then passed on to their children, who adopt a similar attitude to people who are not part of their social group, they display aggressive and disrespectful behaviour, as you have experienced, because that underlines their alienation and increases their bond with each other. Add in the normal attitudes of adolescents, and their approach becomes magnified, again as you have sadly experienced.
Education would be the answer, but that is unlikely. given the inherent distrust of travellers for the community at large, so they remain a challenge to the rest of us, and perversely proud to be so.