It would be like redefining "terrorist" to mean "airline passenger." Some airline passengers are terrorists and some aren't -- indeed, some battle the terrorists. The two have nothing to do with each other, although, sometimes, both notions come together and you get an airline passenger who's a terrorist -- and blows up the plane.
It makes as much sense to say, "Republicans say they're against 'judicial activism,' but conservative justices strike down laws more than liberals do!" as it does to say, "Republicans claim they're against terrorism, but they fly more than Democrats do!"
As former Chief Justice William Rehnquist described the proper role of judicial review in a constitutional democracy, the courts have the last word "as to whether a law passed by the legislature conforms to the Constitution."
It would be every bit as "activist" for the Supreme Court to refuse to strike down a law that violated the Constitution -- e.g., Chicago's anti-gun laws or Congress' restriction of free speech via the campaign finance laws -- as it is for the court to strike down laws that do not violate the Constitution.
We know that laws restricting speech and the right to bear arms violate the Constitution because it says so. The very first two items in the Bill of Rights prohibit the government from infringing on -- I quote -- "the freedom of speech" and "the right of the people to keep and bear arms." You can look it up yourself.
If Congress passed a law banning books critical of the Supreme Court and the court refused to strike down that law, that would be "judicial activism."
Historically, judicial activists have preferred to strike down laws that are perfectly acceptable under the Constitution than to let unconstitutional laws stand. Constitutionally permissible laws include laws against abortion and laws providing for the death penalty.
We know that laws prohibiting abortion do not violate the Constitution because neither abortion, nor its synonyms, nor anything vaguely resembling abortion, is mentioned -- much less granted protected status -- by the Constitution.
And we know that laws providing for the death penalty are permitted by the Constitution because it goes on and on about capital crimes. The Fifth Amendment, for example, says:
-- "No person shall be held to answer for any capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury";
-- "nor shall any person be subject for the same offense to be twice put in jeopardy of life or limb";
-- "nor be deprived of life, liberty, or property, without due process of law."
States are free to ban the death penalty on their own, but the Constitution requires only three things for the imposition of a death sentence: a grand jury indictment, no double jeopardy, and a hearing. The End. Love, the Founding Fathers.
And yet, the Supreme Court banned the death penalty -- even with those three safeguards -- as "unconstitutional" from 1972-1976.
Several justices -- including Kagan's mentor, Justice Thurgood Marshall -- continually voted to ban the death penalty, despite the fact that the Constitution clearly, repeatedly, unquestionably provides for capital punishment.
That's how liberals "get some things done." That's judicial activism.