That is just what the GAL stated "the best interests of the children" in order to get her motion through. However, if you read the article an Indiana law professor himself did stated that it was unconstitutional and if you read the law I quoted this is a problem on a Federal level. I may not be a lawyer but take a look at this, article 1, Section 9 of the Indiana Constitution states:

No law shall be passed, restraining the free interchange of thought and opinion or restricting the right to speak, write, or print, freely, on any subject whatever; but for the abuse of that right, every person shall be responsible. Accordingly, Section 9 expressly extends protection to speaking, writing or printing “on any subject whatever.”  case law in Indiana  “affirms the rights of expression in language more comprehensive than the First Amendment.”

So if Indiana allows that a teenager screaming vulgarities about the school policy about piercing is deemed to be protected under Indiana then a man complaining about how agents of the state in their capacity as state workers wronged him and his family should also be protected. This protection should not be based upon whether he is suspected of any foul action, nor should it be based on "the best interests of the children" as gaged by the State. He is still their father and still innocent in the terms of the law, so he should be allowed free speech.