Does the Confessional Calvinism rule Arminianism as a heretic teaching?

In order to answer whether "every Calvinistic confession that adheres to Dort automatically/logically implies Arminianism is a repackaging of heretic Pelagianism" or not, there is a great need to understand why many people today who come under the umbrella of "Calvinism" misunderstand what they are supposed to believe about heresy.

A huge problem is that the very word 'heresy' is politically (and religiously) 'incorrect' these days. It is so frowned upon that Christians almost never use the word, especially those who have adopted a modern, loosely evangelical but dreadfully sloppy approach to what they are supposed to believe. This is due to an amalgam of old heresies appearing in modern guise (and not just variations on the old Pelagian theme). Because so many Christians have never studied the history of the Church, especially in the first few centuries, they have no idea as to what totally unacceptable ideas the Church had to stand up against, to expose as being heretical. The 'Confessions' from the Reformation onwards did, indeed, call Arminianism a heresy, and that stance should still hold today. Here are what some modern Reformed writings say on the matter. First, let me spell out what words and phrases related to the question mean:

The Heidelberg Catechism was a Reformation document with a question-and-answer format used to teach Christian doctrine and practice. It was written by Caspar Oleviannus and Zacharius Ursinus (1534-83) and approved by the Synod of Heidelberg in 1563. [Many modern Calvinists have never gone through such Catechisms.]

Pelagianism was a school of thought named after Pelagius (354-418?) and promulgated by Julian of Eclanum (c.386-c.455). They taught that the human will was capable of spiritual good without the aid of God's grace, and that sinless perfection was possible in this life. Augustine and Jerome were chief critics of Pelagianism, and it was condemned by church councils in 418 and 431.

Arminianism was initiated in the 17th century, following the teachings of Jacobus Arminius (1560-1609). He emphasized that God's election [choosing] is conditioned upon foreseen faith, his grace can be resisted, and Christ's atonement was made on behalf of all humanity. The first confessional statement of Arminian theology is in the Remonstrance (1610), to which the Synod of Dort responded with its Canons, later known as the Five Points of Calvinism'. (All taken from the Glossary in Pilgrim Theology, Michael Horton, Zondervan, 2011)

From another modern Reformed book comes this definition of heresy:

"Heresy was belief and teaching about God, Jesus Christ and salvation that threatened to distort the gospel message and the Christian life so severely that it could become 'another gospel' and another religion, not the one taught by the apostles." (The Story of Christian Theology p149, Roger E. Olson, Apollos. 1990)

The New Testament itself speaks of some first century men in the church as being heretics, preaching "another gospel which is no gospel at all" (Galatians 1:6-9). Paul also warned of "false apostles and deceitful workers" (2 Corinthians 11:13-15). Jude further condemned "certain men crept in unawares... turning the grace of our God into lasciviousness, and denying the only Lord God, and our Lord Jesus Christ" (verse 4). Heretical teachings were a threat to the integrity of Christ's Church back then, and in every century since. Today there are many old heresies that have just been 'clothed' in modern garb but many Christians have no idea. They have been allowed to slip into the Church by leaders either unaware themselves, or sympathetic to such heresies.

However, the Reformed tradition has always had and continues to have leaders who speak out against not only the heresy of Arminianism (as an adaptation of Pelagianism) but others, such as modern versions of the heresy of Arius. Sadly, if you did a poll of modern Calvinists you might find many of them unable to give clear definitions of the words and concepts this question asks about.

However, I would point out that Spurgeon was a Calvinist. Here is a quote from a Reformed booklet. After listing many Reformed leaders through the centuries, it says:

"Well did that prince of preachers, Charles Haddon Spurgeon put it when he said, 'I have known men bite their lip and grind their teeth in rage when I have been preaching on the sovereignty of God... the doctrinaires of today will allow a God, but He must not be a King.' ...'We are cried down as hyper,' he could say, 'scarcely a minister looks on us or speaks favourably of us; because we hold strong views upon the divine sovereignty of God, and His divine electings and special love towards His people... The old truth that Calvin preached, that Augustine preached, that Paul preached, is the truth that I must preach today, or else be false to my conscience and my God. I cannot shape the truth, I know of no such thing as pairing off the rough edges of a doctrine. John Knox's gospel is my gospel; that which thundered through Scotland, must thunder through England again'." (The Five Points of Calvinism, pp23-24, W.J. Seaton, Banner of Truth Trust, Edinburgh Scotland, 1979, reprint 1984)

The answer to the question whether "every Calvinistic confession that adheres to Dort automatically/logically implies Arminianism is a repackaging of heretic Pelagianism" or not, is a clear Yes. But you will not get such clarity from many of those today who appear to be under the umbrella of Calvinism, yet who have not been vigilant to maintain the purity of the biblical gospel. The less the Bible is regarded as the inspired word of God, and the more it is tampered with by modern translators, the worse this corrupted gospel will become as heresy gains a foothold.