No, it's not taboo. However, most people who follow the path of witchcraft do not subscribe to the Christian version of God. Some are atheist, others, like me, believe in a great ocean of universal energy. Many prefer to rename God as the Goddess. Or as a duality of both. In witchcraft and paganism, there is no agreement on what this source energy should be named. And that's how we like it.
Having said all that, there are many Christian witches who have been able to reconcile their faith with their path and acknowledge the Christian God as the source of their power.
You mention 'gifts'. Every single human has gifts of one kind or another. If you are referring to psychic abilities, that doesn't make someone a witch... it makes them a psychic. They are only witches if they practice witchcraft.