Michael Bolton demanded an apology from Tonioli after the judge called his performance a "doggy mess" and said that it was "the worst jive [he'd] ever seen".
However, Osbourne, who finished third on the ABC competition in 2009, said that Tonioli was just "doing what he gets paid to do", according to People.
"I thought that Bruno was really harsh on Michael Bolton, but when you watch it you can understand why he was really harsh," she admitted.
"[Bruno's] a judge, and that's what he gets paid to do. He's the shock jock of the judging panel. Yes, he was hard, but don't go on a show where you have to judge if you don't want to be judged!"
Bolton's professional dance partner Cheslie Hightower, current DWTS competitor Audrina Patridge and former runner-up Mel B have all criticised Tonioli's comments.
Dancing With The Stars airs on Mondays and Tuesdays on ABC.