That percentage became less disturbing for me once the article broke it down by age groups:

"For example, while 93 percent and 67 percent of 9 year olds said that they believed Robovie to be intelligent and to have feelings, respectively, those percentages drop to 70 percent and just 43 percent when you ask 15 year olds the same thing. Older children were also much less likely to think of Robovie as a friend, but more likely to object to a person being able to sell Robovie."

As children get older, they understand that Robovie is not a friend but they object to selling an intelligent being. I think this just implies that younger children don't understand the concept of slavery as a violation of basic human rights.