I haven't edited this, but this will give you a sense of what I say.
When they’ve heard about the policy and 1978 and all that I always start with something like:
“I’m just speaking for myself here, but the policy was racist, was an affront to God, should never have happened, and I’m appalled that it lasted as long as it did. If you want to discuss the details, I’m someone who can do that with you, but if you’d rather not, that’s great too.”
The conversation often goes into things like:
1. Quotes that investigators have found on the Internet. The fact that I pull out the quote for discussion builds credibility like you can't imagine.
2. Church leaders were reading their own cultural biases into scriptures (I like to bring up Peter’s struggle with Gentiles. If Peter could discriminate, anyone can). They were drawing on folklore and racist stereotypes prevalent among many whites.
3. “There is a residue of racism in the Church, most all of it at the grassroots level. Some of the members have older books on their shelves that still have racist statements here or there, and the way one Mormon or another thinks about the racist policy might not sit well with you. There’s been no official explanation. The topic comes up occasionally, and once every four years in Sunday School, but most everyone will be sensitive about the subject. Many Mormons, and especially North American and white Mormons, have a strong desire to overcome the Church's racist past. You won’t encounter a lot of racism in the Church today, but you can expect a little. A few people might be unintentionally racist out of a misguided desire to purge their own guilt (someone might ask you about Ebonics or Southern food at a ward picnic, but what they’re trying to say is “You’re black and that’s OK with me.” They don’t usually see that they’re stereotyping.) But those situations will be few and far between. The overwhelming majority of Mormons will be loving and kind. They’ll have you over to their houses for dinner and greet you warmly when they meet you in public (a big issue for black people is white people’s two-facedness). You’re likely to have callings where people of all races will be assisting, sustaining, and working right beside you.”
4. The following as per the investigator's concerns: Joseph Smith’s more open views, the issues under McKay’s presidency, Walker Lewis and Elijah Able (and the exemption of Able's descendents from the ban), the early believers in Nigeria, the events surrounding the Sao Paulo temple, James E. Faust’s service in President Kennedy’s racial harmony coalition, Hugh B. Brown’s opposition to the policy, changes to the 1981 edition of the BoM, the article against interracial marriages that was front and center in the issue of the Church News that “announced” the 1978 revelation by burying it in the back (revolting, that), Spencer W. Kimball and so on.
5. I recommend the Genesis Group and steer them to supportive Black and Mormon websites if they seem interested.
I highly recommend Mauss' article: "Dispelling the Curse of Cain: Or, How to Explain the Old Priesthood Ban Without Looking Ridiculous." Just click on the article's title (you can even print it!):
http://www.sunstoneonline.com/magazi...-issue-134.asp
I also recommend the books:
Black and Mormon--Bringhurst & Smith
All Abraham's Children--Mauss
There's a ton of great Dialogue (especially Lester Bush) and Sunstone articles too, but I'll let you search for those.