The cauldron us used to symbolize the womb of life. Candles serve several purposes, they provide light, they represent deity, and they can symbolize a need in a spell, to name a few. Salt represents the Earth, and Water, the water of life. Wiccans do not feel that the life of another creature is ours to give therefore we would never kill an animal in ritual, as we would not consider it a sacrifice. Wiccans also believe that the Goddess is the Mother of All Life, so why would she want the destruction of one of her own creations.
Spells are just active prayers.
Spells, much like prayers, are used to as a catalyst to create change in one's own life or the life of a loved one. Prayers are a petition to Deity to create the change. Spells are are used to connect with our own divine selves, and use our own energies to create the change. Anything manipulative that goes against the free will of another is considered wrong. A cult by definition is a group of people who blindly follow a leader.