So what have they done wrong?
Where to begin. Where do they dispose of their sewage? Where do they dispose of their household rubbish? Where do they dispose of the rubbish they have been paid to collect?
“If its private property then they are trespassing and there is a law that covers that.”
Unless it’s criminal trespass (which it isn’t) their occupation of the land is purely a civil matter. It is notoriously difficult to evict somebody from private land and involves court orders having to be sought and actioned. The police play no part in this process and will only attend, if asked, to keep the peace when private bailiffs attend to carry out the writ (at a cost to the landowner). To understand this, Islay, imagine you owned a small field which you used from time to time. If travellers pitch up on it you will have to go to the Court, explain why you want them moved, obtain a writ of possession and then either serve it yourself and hope they obey it or pay bailiffs to serve it on your behalf. Fair?
There is no justification for treating travellers with special dispensation. They chose their lifestyle and so must deal with the attendant inconveniences that go with it (such as, er…continually having to travel). But they want no part of mainstream society.