The previously taped segment, which finally aired on Wednesday's episode, showed Giuliani popping out of a jack-in-the-box while performing a rendition of Bad to the Bone.
"This is definitely something I never would have guessed," panelist Robin Thicke said in shock. McCarthy and Scherzinger enthusiastically got out of their seats to dance and sing the lyrics while Ken Jeong stormed off stage in protest, stating, "I'm done."
"I hope the world doesn't soon forget @NicoleScherzy and @JennyMcCarthy being hype girls for the beyond disgraced Rudy Giuliani," one naysayer tweeted after the viral moment aired. "@kenjeong had the only rational and reasonable response to this. Shame on @MaskedSingerFOX for giving Giuliani a platform."
"I can't with those two women anymore. Shame on them. Shame on the show," another viewer griped, while a third social media user who witnessed the awkward moment added, "Much respect for Dr. Ken Jeung. Not surprised at Jenny and Nicole; disappointed with Robin Thicke and the entire #TheMaskedSinger management."
Meanwhile, others defended McCarthy and Scherzinger for still "staying professional after the reveal and carrying the show." Another agreed, writing, "I'm glad Nicole, Jenny and Nick had the decency to be polite to Rudy Giuliani."
"Ken was super upset and indeed stormed out," an insider previously told PEOPLE. "Robin actually followed him because he and Ken are very close friends, and he wanted to check on him. Robin didn't storm out because of Giuliani."
Giuliani later told host Nick Cannon why he joined The Masked Singer this season. "I just had a granddaughter, Grace, and I want her to know that you should try everything, even the things that are completely unlike you and unlikely — and I can't think of anything more unlike me and unlikely than this," he shared.
Giuliani, who was a lawyer for President Donald Trump, was recently subpoenaed in January by the House select committee investigating the Capitol riot for pushing "unsupported theories about election fraud" and efforts to "overturn the election results."