Javert snorts at this summation of the poem, and shoots Prouvaire a dark look for his comment about watching Bahorel's face. His job is to notice details! Trust people like this to make it seem like a bad skill to have.

'It was endless, mindless dross,' he mutters.

TO BE FAIR, he would think that of anything that involved fairies, because such things are ridiculous and not worth the effort it takes to write about them. Never mind that they probably exist in this place, they are not real at home, and therefore do not count as a valid subject for writing.