Point taken, but one could argue the opposite - that if God really IS the one and only supreme power, then we MUST accept that he COULD remove all power to chose, because if we insist on humanity's right to choice, then we're insisting on taking that power from God.
This is what Calvinism says - in order to believe that God really is the one and only power, you have to believe he could predestine everything. Now where people get confused is that Calvinist do not say that "GOD HAS PREDESTINED EVERYTHING", no we're just saying that because he is God, he could. Most Calvinists also understand the distinction between "freedom of the Will" and "freedom". You can believe that one's Will is not free and still believe people have been granted the power to make their own choices. The Will only refers to one thing - whether or not you have God's Grace in your heart. A Calvinist's concept of the Will does not refer to making choices like "what should I wear today?", "who should I ask to the dance?", "should I watch this movie?", etc.
Neo-Calvinists and surface level Calvinists who've never taken the time to study Calvinist theology at length will believe or allow people to believe that freedom and freedom of the Will are synonymous.