"They're brainless, whoever thinks that," Wolff told reporters when asked what he would say to those who believe Antonelli is being given advantageous treatment.
Antonelli, who is running an upgraded car on the Marina Bay Street Circuit, has won eight races this season to his luckless teammate's three.
He leads Russell, who retired at last week's race with a failed engine, by 84 points going into the Singapore Grand Prix, where a penalty for going through his regulation four engines will put Russell at the back of the starting grid.
Favouritism is "completely nonsensical," Wolff said.
"I've always tried since I came into Formula 1, even in my Williams days, to be the most balanced and the most transparent with the drivers," he said, recalling a conversation years ago on the grid with Alain Prost about his arch-rival Ayrton Senna.
"I said: 'Just out of interest, why did it go so wrong between you and Senna?' And he said: 'Because we never knew what the team was about.'
"So, I took it as my challenge to keep it always balanced. And it was not easy with Lewis and Nico back in the day," he said, referring to tension between then-teammates Lewis Hamilton and Nico Rosberg at Mercedes under Wolff a decade ago.
This week, the team has reverted Russell to an older car setup in Singapore and he set the fastest time in Friday's practice session.
"We have had Kimi since he was 11 ... (and) George, who's been with us since he was 17," said Wolff. "We are very close.
"That's why it's pretty annoying to have some lunatics that have no understanding, really, about how relationships work, coming up with these kind of accusations.
"Most important is that George knows how the team is and Kimi knows. We will always try to give them equal opportunity, and when it comes to the upgrade, it's a good example - we don't know which one is going to be quicker."