I too believe Christianity and Wicca are mutually exclusive.
One of the reasons God forbids magic/sorcery and all that pertains to it, is because it is a counterfeit. Example: when Moses stood before Pharoah, Pharoah's magicians had a little duel with Moses. At first it seemed they could do the same "tricks," until Moses' snake swallowed up their snakes, demonstrating God's supremacy and power.
Certainly people can attempt to use magic for good, and I have no doubt those who are professing pagans on here want only to do good. So I would never say all Wiccans are evil people who are going around casting dark spells. However, I would say that pagans are misled as to where that power to do magic comes from. Certainly it often resembles the power displayed by Christians, as some have pointed out. But that does not mean the power comes from the same source. It is a counterfeit power, that does not glorify God (as fascist crusader pointed out), therefore God hates it.
I don't mean to offend anyone, but those are my beliefs as a Christian.