I think this may be an issue with the English language rather than "some who claim to be Christians". Actually, in Hebrew and Aramaic, the Holy Spirit is feminine. In Greek, neutral.
I had an acquaintance from Eastern Europe a while back and she kept saying "she" when talking about the Holy Spirit. We did ask, and she kept apologising - but explained that in her langauge the Holy Spirit was female, she was just translating in her head. In her Bible, the Spirit was "she". In Genesis for example you can translate it as "the Spirit of God she was hovering over the face of the waters"
Now that isn't to say that the Holy Spirit is female. We mustn't confuse God's chosen language of revelation (Father, Son, etc) with gender. God is spirit, and men and women are created in God's image.
So, for me, it comes down to respect. If I tell you my name, Don, and you decide you don't like that name because of another Don who mistreated you, would it be legitimate for you to decide to call me something else? That would be disrespectful. In the same way, God revealed himself as Father, and Jesus the Son - so "Mother" is disrespectful. Jesus is, well, Jesus. I have less of an issue with someone using "she" for the Spirit though where that's a language issue.