Opetaia, 28, told Main Event TV he had been forced to vacate his belt as Zorro is not the IBF's number one contender.
"It's very short-sighted of the IBF if they go down this road," Warren said.
"Everybody on board, including the number one [mandatory challenger Mairis Briedis], were all happy for it to take place," the veteran promoter told BBC Sport.
"But, you know what, the fight is going on.
"Everybody knows who he [Opetaia] is, they know he's considered to be the best at his weight out there so we'll just get on with it and the fight will happen.
"It's too big a fight not to happen and it's too big an opportunity for the fighters not to fight.
"It [the IBF's decision] is ridiculous really."
Australian Opetaia beat Britain's Jordan Thompson in September with a brutal fourth-round stoppage.
"They've [IBF] really left me with no choice," Opetaia told Main Event TV.
"This is a massive card that I can't say no to so they've stripped me. It is what it is.
"They can do what they want. I'll get the belts back. All I've got to do is to train hard, keep winning and they'll come back to me."
https://www.bbc.co.uk/sport/boxing/67747489
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