the craft is around is nature and what is in this world.
That is the crux of the matter. Islam and Mormonism are high concerns of many Catholic apologists because of the danger their spread faces poorly-educated Catholics. Sheep-stealing, we call it.
But the reason Wicca is derided if not outright reviled is that, unlike Islam and Mormonism, Wicca does not seek union with something beyond. It is a religion steeped in nature, in creation. While I admire anyone who appreciates creation, it is transient and God is beyond the physical world. Beyond that more esoteric understanding of Wicca, it is my understanding that many believe in reincarnation, and their understanding of an “afterlife” is only a stopping point between lives. Their focus is in the world, and living “for the world” is opposed to Catholic teaching in which we are to live
in the world but not
for it. There is an aesthetic self-denial intrinsic to Catholicism that is absent in Wicca. Yes in Wicca you cannot go about killing anyone you want because self-gratification is not encouraged, but Wiccan theology is bound to the world, and the only way to properly celebrate it is to indulge in the world.
Islam and Mormonism both teach a focus on the state of your soul and the eternity that awaits it. So while their worldly practices and theology are ultimately threatening, they are at least looking in the same direction as Catholics (generally speaking, I know a lot of CAF’ers that will start flaming me for saying as much), but Wiccans are looking in the opposite direction. Because Catholicism identifies their focus with God, by extension, we view Wiccans as staring Satan in the face and welcoming him with open arms.
That’s why it comes up in irrelevant threads and that is why it’s one of those big concerns of Catholics. It’s relative minority status, however, means that it does not have the urgency of Islam or Mormonism.