Its an interesting argument put forward by the author - but I'm going to call it out for the virtue signal it is.... if energy is the pre-requisite for playing the character, and truthfulness to the books is a secondary factor, then couldn't this part be played by anyone at all? Why have they picked a young girl at all? If it doesn't matter what race of actor they pick, why didn't they pick a boy? Or why not pick an elderly man? Fuck it... why not have the Rock?

Let's examine this statement... you are upset/disappointed/frustrated/angry because a 6-feet plus tall muscular behemoth was cast as a character who was described as a small girl in the books. You are judging Dwayne Johnson's appropriateness for this role on his sex/race/age and size. He is a well hewn chiselled man playing someone described in the books as a small white girl.

Friends, that is sexist, racist, ageist and fattist.

When people don't fit the imagined version they have in their head, it pisses people off. That might be racism, it might be disappointment at having their bubble burst. What matters is that Leah Jeffries was the best actor that came forward and was picked for the role on her merits (I suspect she was) ... but if it turns out she was cast because of the colour of her skin (because someone at Disney wanted to demonstrate how on board with the progressive message they were) and not on the quality of her acting, that'll come back and bite everyone on the ass - including Mr Riordan.