AAAAAAAAAARRRRGGGGGGGGGHHHHHH!
Sorry, but people looking for the hidden dark side in little Anakin I think are missing the point. Somehwat the point of the Anakin presented in TPM is that he was perfect and angelic, so much better to contrast the person he becomes.
ALL his Dark Side emotions are deep-seated and hidden so only the Jedi can spot them. That line is not evidence of hidden anger, it's just him being expressive!
It;s like all those people that think that Greedo fighting scene shows his Dark Side. No, it shows he is a boy who gets into a fight with another that calls him a cheat. Sounds like EVERY boy to me.