First, free will is not Biblical, so therefore it is not true. God is the sovereign Lord, He does what He pleases in the heavens and the earth. There is no autonomous will...no autonomous molecule that is not a part of His predestined decree. I don't "believe" in free will because it is not Biblical or logical.
Secondly, there is an element of determinism in every worldview. My argument isnt against determinism per se, but against the atheist conception of impersonal biological fatalism. God's decree, whereby He accomplishes His holy will, is not fatalism, since His ultimately good purpose is what He intends and fulfills.
Thirdly, yes, I do believe in freedom of thought. In fact, I think Christianity alone provides a foundation for the mind of man to be free. Not autonomous of course, because only God is autonomous. But free from impersonal biological fatalism.
But being "free from impersonal biological fatalism" is not freedom of thought. You're just replacing one slave master for another by replacing biological instinct with the will of God. If you're being forced to think and act in any way by some other force, whether it be instinct or God, you do not have freedom of thought.
Free thought, true free thought, requires mental autonomy. It requires that there me an actual "me" who is defined separately from everyone else. I have to have the ability and power to say he/she believes "this" while I believe "this different thing, or I could thing this different thing but actually agree with him/her." If I cannot do that, then I don't have freedom of thought.
So why don't you say what you mean. You aren't arguing that atheists don't believe in freedom of thought, what you're saying is they need to replace their belief in personal slavery to biological instinct with personal slavery to the will of God.
As for the Biblical truth of free will, we have argued this over and over. There is no point in beating a dead horse. My only comment is that it amazes me that you limit the power of God so much that you think His power or sovereignty are threatened by an autonomous will such as mine. He
could force me to obey His will, but that would not give Him "more power" any more so than my independent mind threatens his Godhood and power.
One thing Calvin was
almost right about. Man is disposed to sin. We cannot save ourselves. If it were not for the Atonement of Jesus Christ we would all end up damned because we follow our baser nature at least once in our lifetime. But because of the Atonement we are saved from that base nature, saved from the Fall's damning effect and made free, free to use our agency (our ability to self-determine and act) to choose Christ and eternal life, having that sinful nature overcome by His sacrifice and grace. As Lehi put it around 600 BC:
"And the Messiah cometh in the fulness of time, that he may redeem the children of men from the fall. And because that they are redeemed from the fall they have become free forever, knowing good from evil; to act for themselves and not to be acted upon, save it be by the punishment of the law at the great and last day, according to the commandments which God hath given.
Wherefore, men are free according to the flesh; and all things are given them which are expedient unto man. And they are free to choose liberty and eternal life, through the great Mediator of all men, or to choose captivity and death, according to the captivity and power of the devil; for he seeketh that all men might be miserable like unto himself." (2 Nephi 2:26-27)