Randy L. Stinson and Christopher w. Cowan in the latest issue of CBMW Journal identify seven reasons why we cannot legitimately call God Mother.
1. There is no biblical precedent for referring to God with feminine terms such as "Mother" or "she."
2. Biblical, masculine language for God is not culture-dependent, but rather is God's chosen self-revelation of his identity.
3. The use of "feminine imagery" for God in the Bible does not demand or even imply that we may refer to God with feminine terms such as "Mother" or "she."
4. All feminine metaphors for God in the Bible are verbal-none are names or titles for God (like "Father").
5. "Father" is a name or title that communicates something real about God's nature.
6. Calling God "Mother" may require an unbiblical revision regarding how God relates to the world.7. Calling God "Mother" calls into question the sufficiency of the biblical revelation.
To read the entire article here.