I first wish to point out that there are many rituals and practices involving the cross that are indeed idolatrous and of an occult nature. It is usually because of these practices that many say the cross itself is an idol. I believe this to be an extreme view. Such a conclusion would mean that the sun itself is an idol, because there are people who worship the sun as a god. Likewise with the moon, the stars, the constellations, the zodiac, etc., all of which are presented in the Bible as being God's creation. God's creation, as such, are not idols, but anything of God's creation can be used as an idol; it is the way such a thing is used that makes it an idol in its usage, not that the thing created is of itself an idol.
We need to note that a form of the cross is used throughout both the Old Testament and the New Testament in the form of a letter of both the Hebrew and Greek alphabet, usually referred to as "Tau" both in Hebrew and Greek. If this shape is, of itself, an idol, then the Bible writers have been guilty of using this idol throughout the Bible. However, the Tau cross was a symbol of the Roman God Mithras and the Greek Attis, and their forerunner Tammuz, the Sumerian solar God, the consort of the Goddess Ishtar. In Latin, this symbol is called the "crux ommissa," and it is a variant of that which is usually called the "Christian cross", the crux ordinaria, believed by many to have been the actual shape of the instrument on which Jesus was hung. Nevertheless, many believe that the shape of the instrument on which Jesus died was that of the Tau, the crux commissa. Obviously, the use of this symbol in idolatry does not, however, make the symbol itself an idol.
On the other hand, because the symbol has been, and even to this day, used in idolatry as well as occult practices, I believe one should be aware of this, and not contribute to such idolatrous practices. Likewise, we do not know for sure that the instrument of Christ's death did actually have a crossbeam, and there are those who argue that it did not, that it was simply an upright pole.
See:
History of the Cross
