When I first heard about feminists complaining about the use of "mankind" for "humankind" and "chairman" for "chair", I thought the issue was ridiculous. I've long since changed my mind, and am a strong advocate for inclusive language.
I remember in university reading a study (which I cannot find!) that showed that an ad for a job placed in a newspaper got more female applicants if the language was gender inclusive. For example, if the ad said, "The ideal applicant will have ... He will be... His experience includes..." less women applied. Whereas, if the ad was inclusive and said, "The ideal applicant will have... He or she will be... etc." more women applied. For me, this was concrete evidence that gender neutral language really did make a difference.
Recently, I noticed that the minister at my church doesn't use any gender-based God-language. That is, she doesn't call God "him" (or "her" for that matter). She's very careful about that. I really appreciate that. I think part of her reason for this is that she, like me, is panentheistic, and doesn't really think of God as a personified deity, except as a comfortable metaphor. I think, anyway. I don't presume to speak for her.
When I grew up, it was in the Catholic Church. I went to Catholic schools in Regina. My Mom is a devout Catholic. Dad wasn't. He went to church with her, but it was only as a show of support. God language was always gender based. We always talked about God the Father. He was "Him". Girls, I felt, could never really aspire to be god-like. I was extremely put off by the sexism in the church, as early as about Grade 3, when we were learning about Mary. I was upset that boys could try to be like Jesus, but girls could really only aspire to be his mother. I was also really angry when I heard about the immaculate conception (that is, the conception of Mary - not Jesus). She was born without Original Sin, a concept I found disturbing from the getgo. So, not only could I only aspire to be Mary, mother of God, I had absolutely no chance of ever getting there because she was born without sin! And don't get me started on the whole bit about her getting pregnant without sex! How livid I was that day! :) And can anyone tell me definitively what the RCC's stance is on her having sex after getting married to Joseph? I know she's called "The Ever-Virgin Mary" in at least one Catholic prayer, but I've heard priests talk about his siblings.
Anyway, back to the point. I found religion (i.e. the only religion I knew) to be very excluding of me and the rest of my gender, not only by its theology, but by its language. I no longer struggle with that. Partially because I found an inclusive church, partially because I recognise that the Bible is a book that reflects the time in which it was written, partially because I simply know that God wouldn't have made half the race inferior to the other half and made it completely obvious by sex organs. It's just ridiculous to even consider.
But I do very much wish for more gender inclusive language. Not only in church (the hymns... Don't get me started!), but in the rest of the world too. I don't think it's asking too much to change our words slightly to make half the population feel more included. And yes, I recognise that some women don't feel excluded by words like "mankind" or generic masculine third persons "he/him/his", but if studies show time and again that women do feel excluded, even subconciously, then what does it hurt to change it? Are we that set in our ways that we can't be reasonably accomodating of people's feelings? How can we expect to grow as a society, to become more enlightened people, if we say, "No, your feelings don't matter" on something as trivial as terminology? I honestly don't think we can.