A controversial European Central Bank paper that stopped just short of calling Bitcoin a Ponzi scheme earlier this month has been slammed by a group of crypto academics in their latest academic rebuttal. The ECB paper “portrays Bitcoin’s volatility, lack of productive contribution, and wealth concentration as critical flaws,” writes author Dr. Murry Rudd from the Bitcoin advocacy organization Satoshi Action Fund. The rebuttal, released on Oct. 22, critiques an Oct. 12 ECB working paper by Ulrich Bindseil and Jürgen Schaaf that caused outrage among crypto advocates. The paper presented a negati…