I don't agree with this. Like it or not, Knox and Sollecito are still on trial for the murder of Meredith Kercher. And, like it or not, it's eminently possible (probable, even) that the Kercher family were persuaded long ago of the guilt of Knox and Sollecito, and that this is a belief that they are either unwilling or unable to give up easily.
I think that the Kerchers should really be saying nothing at the moment, and letting the judicial process take its course. If they want to say things though, that's their prerogative. And if those things are unsympathetic or ever derogatory towards Knox and/or Sollecito, it's probably understandable in the circumstances.
However, if and when Knox and Sollecito are cleared of involvement in Meredith's murder, I would very much hope that the Kerchers will cease making any public statements about the two, other than saying that they respect the judicial process. To me, that will be when their "free pass" on public statements expires. Not a minute before. And I suspect that it may take a good deal longer than that for their private thoughts on Knox and Sollecito to shift from their apparent current positions.