The reasons are already well documented.

See:

• The Truth About WICCA (Witchcraft) - Gives all the details about why wicca is evil and its links to Liberal movements like feminists.
• I was a goddess-worshipping witch. - Confessions from a long time follower of Wicca, who found Christ. In Wicca they advanced so far, that they found out many of the dirty little secrets about Wicca. They also found that it lead them straight to Satanism.

Related post: Witch Wants Wiccan Symbol on Husband’s Military Memorial Plaque