You can be a Christian and a motorcycle rider; you can be a Christian and a chef; you can be a Christian and a witch. Being a witch is something that one does, not something that one is. (Although we often tend to define ourselves by what we do if we're really passionate about it.)
That said, I believe there are ways of doing things that are more correct than others. Intrinsic to most forms of witchcraft is the premise of duality, i.e. that there must be balance and harmony between energies. The idea of god as male-only is an invention of a patriarchal society and abhorrent to most of the pagans and witches that I know; we are biological beings of the natural world and the idea of a male god with no female equal/opposite just doesn't fly in that context.
I really think the most important thing that a person can do is to educate him- or herself about whatever religion(s) they feel drawn to, as well as at least gaining a cursory knowledge of the other religions of the world. Seeing the larger picture is very important for people who choose this path.
Of course these are just my opinions, and I - like everyone else - am merely a humble seeker of truth.
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