Here he chooses to interpret what they say as demanding the recognition of a new constitutional right to safe water and to correct information. It is not at all clear that that's a good choice.
He could equally well interpret the situation by analogy: the government deliberately tricked people into drinking unsafe water, and people were, depending on whether there is evidence of poisoning from the lead, either provably or not provably harmed.
Thus it is open to him to interpret their question as one that is not so focused on novel constitutional rights.