The question that arose to me is whether separating the LDS and the FLDS is reasonable.
Are they really separate religions? Hinduism is treated as a single faith even though it comprises 1.3 billion people divided among dozens of sects. Roughly the same is true of Islam. Is it fair to treat those as unitary religions while simultaneously treating the few million LDS and the perhaps 100,000 FLDS as independent traditions?
And if the two were treated as parts of a single "Mormonism," would the diffusion index (statistical technique of subtracting negative responses from positive to obtain a net figure) not be lower than for just the LDS? If you take an average, you get -24, which puts Mormonism among the least respected faiths in the survey.
What are the odds that the article is reprised in the Deseret News?
That's an interesting point about how the groups are aggregated and/or split up.
For example, the highest scoring group is "christian," but it's also a superset of several of the other groups (Catholic and Protestant). Protestant, in turn, is a superset of several of the others (Methodist, Lutheran, etc).
Also, FLDS is listed, while the Community of Christ (RLDS), isn't listed individually, even though it has orders of magnitude more members than the FLDS. The FLDS are more visible in the news though, so perhaps no one knows who the CofC are. And if they were referenced by name, people would likely not even equate them to a form of Mormonism.
But consider that Lutheranism, Methodism, Presbyterianism, even Catholicism consist of multiple different sects. And as LW noted, Islam is also multiple different groups. They also only list 2 of the many Baptist denominations. The likely reason is that most people don't think about the many different versions of those religions, rather they just think of the larger classifications.
There are many mormon offshoots, most of which are unknown to the vast majority of Americans. Asking about all of them would lead to a lot of responses of "Who are they?".
I think the FLDS were specifically included because they are pretty well known thanks to the exploits of Warren Jeffs.