Argentina were rocked this week by revelations captain Pablo Matera and two other senior players had posted racist comments on their social media accounts more than seven years ago.
Coach Mario Ledesma has omitted the three from his matchday squad for Saturday's clash at Western Sydney stadium to shield them from more criticism after they were targeted by "a lot of hate".
Hooper said the tough week could make Argentina more determined to finish on a high note and the Wallabies needed to be ready.
"They're clearly training well against each other during the week. And they'll be certainly up for it after a week like that," Hooper told reporters.
"They're a passionate bunch of guys and I'm sure they'll be up for the game."
Both teams have a mathematical chance of wresting the title away from New Zealand, though Australia would need to win by 101 points and the Pumas by 93 at Western Sydney Stadium for that to happen.
The weather will be a steamy 28 degrees Celsius with the chance of a thunderstorm, which could test both sides and particularly Argentina, who head into their fourth game in successive weeks.
"They've had four tough games on the trot and even some trial matches before that," Hooper said.
"I think the weather is going to throw a few spanners in the works there ... The team that navigates that well is going to do well on the park tomorrow."
Australia squandered a nine-point lead in the 15-15 draw against the Pumas two weeks ago in Newcastle, and Hooper called for more discipline from his players to prevent Argentina sharp-shooter Nicolas Sanchez from hurting them with penalties.
"We're looking to have a complete performance tomorrow," he said.
"After tomorrow we'll know if we can give a better rating about where our season was at."
Meanwhile former England wing Ugo Monye has criticised the Argentina Rugby Union for rescinding its sanction against captain Pablo Matera, saying the governing body is more interested in protecting its players than in dealing with racism.
Flanker Matera was stripped of the captaincy and, along with lock Guido Petti and hooker Santiago Socino, suspended for comments posted between 2011 and 2013 which disparaged Black people and those from other South American nations.
But the UAR said the players' apologies, combined with their good behaviour in the years since the comments were posted, meant the suspension could be lifted.
"I've been so frustrated," Monye, who was capped 14 times by England between 2008-2012, told the BBC. "Rugby doesn't know how to deal with racism, hence why we have seen a U-turn within 48 hours.
"Racism seems to be this outlier forever because no one wants to own up to it. If you've got the union saying it's immature, that's what they think it is. Just so we are clear, the comments are not immature -- they are racist and vile."
Monye also condemned the abuse Matera received online in response to the comments.
"For those people that have tweeted him and his family - shame on you too," he said. "That is not how we move forward."
"I wouldn't want to be judged on the person I was eight years ago. I'm not saying that's what we need to do with Matera. But I want it to be acknowledged and dealt with in the appropriate fashion.
"The UAR are more interested in protecting their player than they are in dealing with the issue of racism which affects millions of people every single day."