John Paul Stevens wrote the Supreme Court opinion that expanded the Constitution's authorization of seizing private property for "public use" to seizing private property for a "public purpose." And who would define what a "public purpose" is? Basically, those who were doing the seizing. As Justice Stevens put it, the government authorities' assessment of a proper "public purpose" was entitled to "great respect" by the courts.
Let's go back to square one. Just who was this provision of the Constitution supposed to restrict? Answer: government officials. And to whom would Justice Stevens defer: government officials. Why would those who wrote the Constitution waste good ink putting that protection in there, if not to protect citizens from the very government officials to whom Justice Stevens deferred?
John Paul Stevens is a classic example of what has been wrong with too many Republicans' appointments to the Supreme Court. The biggest argument in favor of nominating him was that he could be confirmed by the Senate without a fight.
Democratic presidents appoint judges who will push their political agenda from the federal bench, even if that requires stretching and twisting the Constitution to reach their goals.
Republicans too often appoint judges whose confirmation will not require a big fight with the Democrats. You can always avoid a fight by surrendering, and a whole wing of the Republican party has long ago mastered the art of preemptive surrender.