Honestly, I avoid categorical statements like that because what cons utes judicial activism is never quite clear to me. Is the Supreme Court eschewing stare decisis and holding that Separate but Equal violates cons utional guarantees of equal protection a function of activism? If so, then that's an example of judicial activism being a good thing. Is the recognition that the Cons ution functionally includes a right to privacy a matter of activism? If so, then that's another example of judicial activism being beneficial to society.
I'm also never clear on what exactly cons utes "activism" when it comes to novel cons utional questions (the area where activism seems to worry most conservatives, in my estimation).
For instance, is the Massachusetts Supreme Court declaring that state discrimination against same-sex marriages violates cons utional guarantees when the state has enacted no law on the subject an example of "activism"? I would say that the Court was asked to pass on a legal question that has significant moral ramifications, but one that is not resolved textually by cons ution or statute -- in that instance, our society has accorded the courts with the obligation to resolve those questions, even if the result is unpopular. If the state supreme court declares in that context that prohibiting same-sex marriage is uncons utional, I wouldn't characterize that as activism; it would be a function that is at the heart of what courts do. I don't think the fact that the courts reach a conclusion that is unpopular is evidence of activism, either. I think, in some ways, reaching that conclusion is the converse activism if the law supports the unpopular result; courts shouldn't be looking to recent polling data to determine what the law does or does not say. If the court's conclusion is unpopular, it is for the legislature to change the law, or for the People to amend the cons ution.
Do I think it's a good thing for courts to ignore existing law in reaching conclusions? Sometimes, but rarely. Do I think courts that make decisions that must be guided by an interpretation of the law that might prove to be unpopular are activist courts? Absolutely not.