"An awful amount of time, effort and money are spent on attracting visitors to Northland because tourism is a vital part of our economy. It's worth more than a billion dollars annually," he said.
"The way visitors are treated is fundamentally important because they go back and tell their family and friends about their experience of Northland and if attacks on them are frequent, it has the potential to damage our reputation as a tourism destination."
Northland tourism leader Jeroen Jongejans said overseas tourists were particularly vulnerable as they did not have the support network.
"Safety and security plays a big part in their decision to visit any place and if attacks get out of hand without any consequences for those that target tourists, our reputation would be damaged."
Mr Jongejans said the fact police followed up on complaints and courts took a serious view of assaults on tourists made Northland a safe place to visit.
Justice Toogood said Williams, Mark Nathan and a third person went to the Ahipara foreshore car park about 4am on March 25 last year and began violently rocking the campervan to the point of tipping it over.
An Argentinian man and a female Polish tourist were sleeping in the campervan at the time.
The 29-year-old Argentinean tourist yelled out before getting out of the campervan. He was attacked and repeatedly punched and kicked while he lay on the ground.
He suffered a fractured rib and injuries to his back, torso and chin.
The female tourist also came out and was punched in the face twice, causing her to fall and bleed from the nose.
She suffered a black eye and severe bruising to her face.
Williams grabbed a plastic bag that contained groceries from the campervan before all three men drove away.
Calls for help from the tourists were not heard, but the woman managed to run to a nearby house and raise the alarm.
Justice Toogood said Williams attacked the visitors at night, at an isolated spot, both were vulnerable, and there were attacks on the head.
Of concern to court, he said, was Williams lack of remorse and his attempts at shifting blame on to his co-offenders.
He has 32 previous convictions, including violent offences.
His lawyer Nick Leader said Williams' pre-sentence report was not overly positive but asked the court to take into account the fact his client had completed a drug and alcohol programme while on remand.
Nathan will be sentenced this morning.