ALL who are born into this world WILL sin. It is inevitable. It's a fact of life. No one except the Lord Jesus Christ was able to NOT sin. Calvinists believe that humanity has NO free will. They believe that God chose before the foundation of the world who He would save and who he would not save. Calvinists also believe that, in order for one to get saved, they MUST first be regenerated and then, they receive saving faith.
These are a few of their "false doctrines." The truth be told, humanity WAS created with a "free will" and every human being is made capable of CHOOSING what/who they wish to believe in. Even if someone decides to be an atheist, they've CHOSEN that route of belief. Hence, Calvinists believe that humanity is essentially, a puppet. Calvinists use the Sovereignty of God as their excuse for trusting in this false doctrine. I like using the following Scripture verse as proof of humanities free will: Matthew 23:37 "O Jerusalem, Jerusalem, thou that killest the prophets, and stonest them which are sent unto thee, how often would I have gathered thy children together, even as a hen gathereth her chickens under her wings, and ye would not!" You'll notice that Christ's desire is to embrace His chosen people (The Jews) however, their "free will " was to CHOOSE not to worship and follow after Him. Christ is, God in the flesh, therefore, He speaks of the Old/New Testament Jews. At times (In the Old Testament) the Jews would walk away from God and follow after idols. That was an example of their free will.
Yet, Calvinism INSISTS there is NO "free will." We see the "free will" of humanity throughout the Old/New Testament. Calvinism changes the character and intent of the God of the Bible in order to have Him fit their false doctrines.