The actress appeared on the U.S. show's 23 July (09) season finale, to perform a singing and dancing tribute to Judy Garland.
While many experts praised her rendition, others were more critical and members of the public, critics and fellow dancers posted scathing reviews online.
One wrote, "She tried to mimic Judy Garland but didn't come close.
The snipes prompted show producer and judge Nigel Lythgoe to take to the internet himself, in Holmes' defence.
He wrote on his Twitter.com page, "I'm trying to figure out why Katie is being judged as a dancer. When a (baseball) star throws out the opening pitch no one says, 'Ooh, crap pitcher.'".