Actually, if you read the pertinent documents, the hairbrush was acquired under court order, and it was misrepresented as Caylee's hairbrush. It is labelled Caylee's brush, not a shared one, or one belonging to another person. The As, in this case, hinder the identification of Caylee, while LE searches for her body.
Meanwhile, the washing of the pants is just as likely an attempt to get rid of evidence that might have aided in the search for Caylee's body. They may have had her DNA, stuff from the environment like dirt or garbage that may have given some clue to her whereabouts.
So, yes, both of these acts by the As are suspicious and could hinder/delay the investigation into recovery or identification of Caylee's body. The hairbrush incident, where Cindy defiantly lied through omission, certainly makes their job more difficult. Saying that, well, Cindy did give them Caylee's hair is beside the point. At the very least, the As have shown themselves to be unco-operative liars and most thinking people would ask themselves why.
And while we're splitting hairs, you in turn ASSUME that the As did not know anything by the time of the stolen gas cans. People infer many things from behaviour, IMO, and inferring that the As' behaviour is kinda suspicious and that they may have known something/are hiding something I don't think is a gigantic leap in the dark. It may not be true in the end, but it is a fair inference.
My guess is that given their behaviour over these past months that the As might be accessories after the fact.
