If there is such a thing as Judicial Activism (judges overstepping the bounds of their authority in order to change the law with far reaching political and social consequences) then this is a clear-cut case. So if you're that guy, who is always harping on how judicial activism is ruining the country, then this decision had better loom large in your view of mistakes made by the US Supreme Court.
You see the way the Supreme Court was designed - as an appellate system - limits the scope and power of Supreme Court decisions, insofar as the Supreme Court can only exercise their power if a question of constitutionality is brought before them by another party. This important check on the Judiciary which is built into our constitutional system serves to help prevent so-called "activist" judges from interfering too often in the process of law-making. Unlike Congress, the judiciary doesn't have general law-making power and can't just change the law whenever they choose. Regardless of the constitutionality of any law or set of law, SCOTUS can only change law through judicial review if the problem is large enough to percolate all the way up the appellate process without fizzling out in one of the many appellate courts. If a constitutional question never reaches them, then no big deal, the popular will expressed through the US Legislature holds. This system seems to work pretty well for the most part.
This is why the decision rendered in Citizens United, which ruled that large portions is so problematic. The question of the facial constitutionality of