Rationale

United States v. Lopez, a recent relevant case, says Congress may regulate "activities that have a substantial relation to interstate commerce ... activities that substantially affect interstate commerce". (Lopez decided that the Gun-Free School Zones Act of 1990, making possession of a firearm in a school zone a federal crime, was not a valid exercise of Commerce Clause authority.) As with Lopez, this case does not directly involve any kind of economic activity nor is it limited to things that have a special connection to interstate commerce. And while in this case the Congressional record finds that such activity, in the aggregate, has an impact on commerce, allowing Congress to regulate everything that had an "attenuated effect" on interstate commerce would essentially remove all limits on what Congress may enact.

As for the Fourteenth Amendment, Congress did have evidence that there was a bias that could deny victims of gender-motivated crimes equal protection of the laws. However, Congress refrained from correcting the problems that denied equal protection, and instead created an additional way to punish the criminals themselves. This causes two problems. First, the Fourteenth Amendment limits itself to states and state actors, of which the criminal is neither. Second, Fourteenth Amendment legislation must have a "congruence and proportionality between the injury to be prevented or remedied and the means adopted to that end" -- additionally punishing criminals for the faults of the judicial system lacks the required proportionality.