I wouldn't place too much value on what was quoted in the article.
Well, of the 4 statements made:
Tonga’s domestic airline fleet currently includes an MA-60 aircraft.
This aircraft has been involved in a significant number of accidents in the last few years.
The MA-60 is not certified to fly in New Zealand or other comparable jurisdictions and would not be allowed to do so without a thorough certification process under Civil Aviation rules.
Travellers utilising the MA-60 do so at their own risk.
2 are undisputed facts (Tonga
does operate an MA-60;
no aircraft gets to carry pax in NZ, or indeed in most countries, unless certificated - which the MA-60 isn't)
1 is arguably true (6 hull losses in less than 5 years)
and 1 is simply a recommendation (albeit a prudent one IMHO)