Why are conservatives against so called "judicial activism" when we've had court cases that have resulted in?

The entire purpose of the court is to evaluate whether laws are consistent with the language of the Constitution, not the "goals" of the Constitution as determined by some judge. It's a fine line, but judicial activism occurs when the Court starts with a desired outcome, and then fashions an opinion that justifies that outcome. The cases you mentioned were correctly decided even though they represented a departure from past decisions.