Pink Taco, a restaurant with a penchant for garnering national publicity with its salacious name, stationed the painted donkey outside its Westfield Century City mall door as a promotion.
The restaurant's spokesman said two animal handlers were with the donkey all day and the animal was comfortable, not mistreated and appeared happy.
About two dozen protesters wanted the restaurant to apologize.
"It was shaved, it was dyed and it was transported like cargo," said Marina Lee of the Companion Animal Protection Society, or CAPS.
Carole Davis, speaking for the CAPS, said "We think that it's in very poor taste at best and we're concerned that it was abusive to the animal."
Davis said the donkey may have been shaved and suffered skin irritation from the paint.
"If you don't think there's anything wrong with it, then go naked, paint yourself pink and tie yourself outside in the hot sun and see how you like it," Davis added. "If you think that it's comfortable, then why don't you volunteer for the job?"
Restaurant officials could not be reached for comment.
"I don't think it was that big of a deal, but I think protesters have a right to do that," said Andy Reed of Century City
Pink Taco's owner has used the news media and protests about its unusual name in past years as a marketing tool. Plans to expand the original location in Scottsdale, Ariz. were derided by that city's mayor because the name is a crude euphemism for a female sex organ.
The restaurant parlayed that flap into appearances on "The Daily Show" and "The Tonight Show Starring Jay Leno."
City News Service contributed to this report.