That's such a bullshit clickbait title. It's well established that fluoride can be neurotoxic at high enough concentrations but the study that this article is indirectly referencing is a study by chinese researchers that concluded:

The results support the possibility of an adverse effect of high fluoride exposure on children's neurodevelopment. Future research should include detailed individual-level information on prenatal exposure, neurobehavioral performance, and covariates for adjustment.

https://www.ncbi.nlm.nih.gov/pubmed/22820538?dopt=Abstract

It in no way states it's on the same level of toxicity as lead, arsnic or murcury.