It turns out that the International Astronomical Union, which voted Pluto out, consists of a relatively small number of the world's astronomers. Others, that were not present at the vote, are calling into question the IAU's authority to make a decision of this magnitude.
A movement of laypeople has appeared to challenge the IAU's ruling. Many are just joking. Some seem really serious. Others just want to cash in. I think the main motivation is just the fear of change. They don't want the solar system they grew up with to be redefined. Some just seem worried about enormous piles of obsolete science textbooks.