Calvinism is a systematic belief system that is centered on the the very purpose of human existence, to worship God.
Calvinism's theology is God centered, mans salvation is only important in so far as such salvation is the will of God and glorifies him. Calvinism's worship is God centered, in accordance with God's instructions and directives.
It is possible for a Christian to have honest disagreements with Calvinism, after all Calvinism is merely an attempt to follow the teachings of Jesus Christ and undoubtedly elements of the Calvinistic structure are mistaken, but hopefully such elements are minor and any error is momentary honest error as a result of mans sinful nature. The world will condemn Calvinism as it sees its precepts as being both foolish and evil in so far as man is not exalted as the world demands, such condemnation is to be welcomed.
When Christians condemn Calvinism such Christians should make sure that they are not basing this judgment on what they would like to be true, rather than what God has revealed as being true and they are not in truth rebelling against God's sovereignty, they should be sure that they are not rejecting God's revelation to the Jewish people, a revelation that Jesus accepted and specifically stated had not passed away and finally they should follow the advice of the Reformers:
In essentials unity
In non essentials liberty
In all else charity
The reformed view is centered on an acceptance that our salvation is through the atoning blood of Jesus Christ, solely according to the sovereign will of God and not due to any merit in man or through any co-operation between man and God. This belief is held to be essential and the Reformed make no apology for this position, rather we believe that it is the Gospel.
Sola Deo Gloria