You cannot justify one case of fraud by attempting to use another 'potential' instance as your jusitfication for committing your illegal actions.
If MDNO DID commit fraud by lying about their process for their R/S, that is a separate issue to be determined by the SEC or the courts.
BUT... whether fraud or not by MDNO, Scottrade committed and act of fraud, regardless of the situation, and should be punished accordingly FOR that fraud.
It will all depend if the Judge gets taken behind closed doors and TOLD what to rule by the SEC. Otherwise, this one is pretty cut and dry.