[tmoertel]

Note that you are making a casual claim (that junk food lowers intelligence in children) but the paper you cite provides no evidence of causation, only a statistical association between diet and intelligence scores. Further, this association could be caused by the well known fact that parents who are more focused on their child’s well being are not only more likely to provide a diet more in line with health recommendations (less junk) but also more likely to invest in their child’s educational outcomes.

[frankvdwaal]

The parent comment is not making a causal claim. They're pointing out a double standard: "Anyone arguing this is about childhood IQ and wouldn’t similarly ban (not stop mandating, ban) soft drinks, chips and fast food for kids, they’re signalling this is about something other than kids’ health."

In other words, if these people are anti-fluoride because it's supposedly bad for children's IQ, they should also oppose bad food for the same reason. If they don't, the supposed (unproven) health effects are not the reason. That's the point that is made, at least.

[JumpCrisscross]

Yup. We don't have causal studies on fluoride's effects on intelligence, to my knowledge. This is so obviously not about kids' health, but like MMRs, partisan/social identity signalling.