But I'm prepared to defend the assertion:
Unfortunately, the paper's calibration of the proxy composite is defective. The 23 proxies used include lake varve thicknesses, varve densities, varve and sediment organic material (OM), sediment biosilica, ice core 18O depletions, and tree ring widths, and are all from different locations. There is no a priori reason to expect these very diverse proxies to all have the same behavior with respect to temperature, even when normalized. Because not all the proxies are available in each decade, the composite does not have constant composition. As its composition changes, it essentially becomes a different index, which must be calibrated separately to temperature. The authors fail to do this, and hence the reconstruction is invalid.
And I believe that if you will not argue based on the facts, you self define as an intellectual coward.