Former rugby league star Hopoate repeatedly held on to Cameron and did not pull away to box, forcing Australian referee Malcolm Bulmer to disqualify him early in the second round. Bulmer had warned Hopoate several times for the offence during the first round.
An angry Hopate swiftly departed the ring after the decision while Cameron's camp also believed the fight was stopped too early.
It was Cameron's return to the ring since his heavy loss at the fists of compatriot David Tua in Hamilton last October in Hamilton. He has subsequently undergone hand surgery.
His professional record now reads 24 wins and two losses.
Hopoate, who played Manly and the Wests Tigers in the National Rugby League, drops to 12 wins and five losses.