I used the words "relatively normal," not "appropriate. It has been known for millenia that 5 year olds tend to act inappropriately.
As for my statement "One could think up quite a few scenerios where the girl might have been responding in a relatively normal - albeit assertive - way":
Those 5 year olds who cannot be baited into either becoming insular and non-responsive, or hysterical are few and far between.
There is a reason that the Biblical instruction for children to obey their parents is side-by-side with the command for parents not to exasperate their children.
Letting a 5-year old have candy and then taking it away can reasonably be expected to result in a confrontation if not done carefully and with deliberation. ...not every child will, but hardly a rare occurrence.
Absolute garbage. A five year old with a normal upbringing would never react the way this child did to that.