Please bear in mind that the following is my opinion, not the opinion of every Wiccan. As it happens, I am a coven priest, yet I do not worship anything or anyone. I respect Divinity, including the gods of other religions.
Many reasons, some of which are mighty controversial. For starters, many people believe that Wiccan ritual tools are used to 'worship' some spirit or another (untrue); this action is specifically prohibited in the Bible. Second, prayer is a request to the Divine, while ritual magick is a direct action with direct results, relying on the practitioner's morality. This is often seen as arrogant, greedy, evil, etc.
Consider the history of the Church. In many cases, when Christianity was forcibly introduced to another culture, the local faith was forced 'underground'; anything having to do with the old religion was proclaimed as evil. Since modern Wicca is a reconstruction of the faiths destroyed by Christianity, many of it's symbols are still considered evil. Especially pervasive is the misguided belief that all Wiccans worship Lucifer; This stems from the following of Cernnunos and other forest deities (represented as having horns or antlers), and the actions taken to stop these 'pagan' practices. By definition, a worshipper of satan IS NOT Wiccan!
One less obvious reason is that Christianity is based on faith, while Wiccan beliefs are essentially scientific. The Pentagram represents the order and balance of the universe as the commingling of four 'elements', or core concepts, unified and guided by Spirit. It is a way of understanding the universe in terms of natural, and controllable, forces. Think of how the early Church would respond to the beliefs of a modern scientist: the likely result would be outrage. It is interesting to note that the traditions of science were carried to modern times from the Greeks (and others) by alchemists and astrologers; both groups.were denounced for challenging the word and power of God.
My last point is that Christianity professes to be the one true religion. Therefore, all other forms of faith are misguided and irrelevant, serving only to keep people from God. From a Christian standpoint, anything that denies people the light and love of God is evil.
Please remember that these things happened a long time ago, and in no way do past events invalidate either faith. Christianity is valid today regardless of past actions. Likewise, Wicca is valid today despite the fact that many mistakenly view it as evil. In sum, it's just a big, messy misunderstanding. Hope that helps.
Edit: Dharmakitten: The practice of magick relies on a scientific perspective. Skepticism is essential; without it, only delusion is left. We use what works, and discard what does not. It is a fluid, evolving faith, suitable for modern times in a way that Christianity is not. Also, no Wiccan I've met would worship any spirit. Communicate with and honor, yes, but never worship. To worship something is to put your life and your future entirely into its power. We must choose our paths for ourselves, never shirking our responsibility to ourselves. To worship anything but life itself is to give up who you are. (That doesn't rule out worshipping some aspect of Divinity, since the Divine is life itself.)
Comments
Many Wiccans DO worship spirits of some sort, and Wicca isn't anymore scientific than Christianity.
by Anon on June 14th, 2005
Christians consider anything that takes their faith from God sin. Faith in majic does just that
by wfbrad on June 18th, 2005
shut up Karma Kitty, you sexually confused, wanna be witch
by Saddened on July 12th, 2005
As Wicca is first and foremost a religion, we do worship spirits. I follow Ma'at and Tehuti, and DO worship them.
by AntigoneRising on December 8th, 2005
There's only 1 God. Wiccanism is clearly Satanism disguised.
by Answers101 on March 12th, 2006
GREAT answer, I learnt a lot :)
To Answers... again...
Satanism is a belief in oneself, not devil-worship, the correct term for devil worship is surprisingly enough, "Devil Worship", Satanism is entirely different to Wicca and devil worshi
by Twhupfold on September 13th, 2006
Buddhists are atheists. Does this mean that Buddhism is "Satanism disguised"? Buddhists are people who turn the other cheek, give to the poor, give up material wealth themselves, and in many other ways *act exactly like Jesus*, but they are in a religion which is "Satanism disguised"? Meanwhile, modern Christianity is all about personal amassing of wealth, hating one's neighbor (often leading to physical violence), refusing to help the poor, and in many other ways *refusing to act exactly like Jesus*, and Christianity is not "Satanism disguised"?
by eternal0void on October 19th, 2007