As regards the question that begins this thread, I admire that the original poster is willing to soldier on in her quest for faith despite the insensitivity and judgementalism of the Christian she spoke with.
I don't use the term "Oh my God." I was raised not to, and as a Christian I feel it's important to use God's name carefully and respectfully, not carelessly. (I do however say "Oh my gosh" all the time, which begs the question of what, really, is the difference. I guess it's all in my mind and heart, which in a sense is what matters most). However, as Irvine pointed out, I know that the vast majority of the people in this world don't think twice about the casual OMG and have no intent to disresepct God or offend me. I really don't think God's pride is so easily pricked and even the commandment (which I would suspect has as much to do with making careless oaths, or oaths which you have no intention of keeping analogous to "swearing on my childrens lives" which you hear on Survivor or Big Brother than expressing emotional excitement) was more for our benefit than because God has thin skin. So I don't worry about it too much, and I hope I would have the good sense not to lecture on this issue to someone who is expressing interest in faith.
As to the comparison to racial/gender/sexual ephitets, I don't think there is any comparison. Nbc keeps talking about intent--well, the use of "Oh my god" never has been and is not now used with intent to to harm anyone (including God). It is at most, carelessness. The other words discussed in this thread both in the past, and in the present have been used with intent to hurt and harm. It absolutely boggles my mind how some posters here cannot see how it might be somewhat acceptible for people to use offensive words in reference to themselves and never acceptable for those outside the group to use the words. (And I say somewhat because there are many blacks, myself included, who do NOT like hearing ANYONE including fellow blacks use "******" or "nigga").
It just seems so obvious to me! Here's an analogy: You know how you can criticize/make fun of your family and it's okay, but let anyone else start in on your family, and your hackles rise? It's like that.