Ramesh Ponnuru at National Review nails it:
"To deploy the rhetoric of activism without regard to the underlying constitutional merits of the question in dispute makes no sense. If the right understanding of the Constitution requires a judge to set aside a statute, then setting it aside cannot be activism. Establishing that it is activism would require establishing first that the understanding of the Constitution that caused it to be set aside was not right. A mere showing that the law was useful, or well motivated, or wide-ranging in its effects, or passed by large margins, would do nothing to establish that the judge was wrong or activist."