Historically, LDS doctrine has changed over time, including notorious teachings regarding polygamy and the fact that, until 1978, blacks were barred from the Mormon priesthood. Mormons may be able to make sense of these changes in doctrine in light of their belief in progressive revelation, but it's difficult for non-Mormons to take "official" LDS doctrine seriously.
If Mormons believe the Book of Mormon is "Scripture", they changed Scripture. The Bible never changes. It may be interpreted differently but the Hebrew and Greek text never changes. As best I can tell, the Book of Mormon is not an interpreted text. The "original" text is in English. So if the BoM is changed via revelation, it is not stable.
The original BoM says "white". It said "white" in 1870 and 1932 and 1960 and it would say "white" today if it hadn't been changed.
I used to be a Presbyterian(PCUSA). When PCUSA ordained women, it was concerned with the pew Bible's version of 1 Tim 3 saying a church leader must be the "husband of one wife". So they changed the Scripture in the pew Bible to "married to one person". It sounds rather similar.
>>Historically, LDS doctrine has changed over time, including notorious teachings regarding polygamy
Notorious? Well, It did bring us notoriety, even though Polygamy is Biblical and was widely practiced at the time, and by a lot more than Mormons.
>> and the fact that, until 1978, blacks were barred from the Mormon priesthood.
Yep, they were. Many were confused when Christ Fulfilled the Law of Moses too.
>>Mormons may be able to make sense of these changes in doctrine in light of their
>>belief in progressive revelation,
Yes, we can, it’s called fait, and the Sprit of Revelation that comes with it.
>>but it's difficult for non-Mormons to take "official" LDS doctrine seriously.
You would probably have had a hard time Taking Jesus “seriously” if you had lived when he was here, since he was revolutionizing things the Jews held so close, like “Blood sacrifices” being replaced with “a Broken heart and a contrite spirit” The law of moses, converts not being required to become circumcised for example. That is supposition on my part, do not be offended, I make no judgment of you, I might well have had a hard time too. I guess we’ll never know for sure.