The problem with judicial activism does not start with with an organized conspiracy to undermine legislative authority. The root of the problem is that judges, like the rest of us, have different ideas as to what the proper role of government is. Even jurists cut from the same ideological cloth can be expected to differ on the details of their role in a representative republic. It is askng too much to expect the judiciary to conform to the opinions of Hamilton, or Madison or Marshall.
Some judicial opinions are obviously infringements on the legislative branch. Federal District Court rulings forcing local governments to raise taxes are good examples, as is the patently legislative trimester framework of Roe v. Wade. Some judges cannot control their tinkering instinct, because they do not see it as improper. Unfortunately, we have no practical mechanism to curb over-reaching by the judicial branch