User blog comment:FairyRaven/Fairy Tail Chapter 325: Unity, Review and Commentary/@comment-4829046-20130329121101/@comment-7418318-20130329141407

-Someone who had surveilance on the king, learned about his secret and is now taking advantage of the kings vulnerbility in the arena.

-Someone who really hates that particular disguise.

-Someone who thinks that the Referee made a bad call in a past tournament and is out for revenge.

-Someone who simply wants to knock the Pumpkin off that persons head to see who is beneath.

... to give just a few reasons ;)