My criticism of sidechains is based purely on them being to convoluted and complex, and also there's the fact that the door is left open for bitcoins to be lost on sidechains which of course would reflect badly on Bitcoin, and be used by the media to launch another tirade of negative propaganda

Also, if the overall goal is for exchanges to become more transparent, then these same exchanges being able to use such a sidechain achieves the opposite. Transparency will bring many obvious advantages for bitcoin