As impartial election administrator, you certainly must. In a democracy, candidates have the right to inform the electorate of their opinions.
If those opinions are widely shared, they will be elected and, if not, they will lose.
If the statement contains any factual error, you might advise the parents of this. If your advice is ignored, so be it.
If you believe, however, that the criticism is unfair, you should rely on the good sense of parents to recognise the fact. To try to refute it yourself would only serve to arouse the suspicion that there might be something in it.