South Dakota went for Hillary in 2008 by 10 points. Let's not disregard that.
She likely only won it because she campaigned there while Obama ignored it and pivoted to the general (sound familiar?)
Besides, she got crushed in a state she won by 40+ points last time, so it seems quite safe to disregard it.
West Virginia and Kentucky do not equal South Dakota. Totally different states with totally different economic situations.
That's true, but I think IceSpear's point was that Hillary only won SD in '08 because she actively campaigned there, while Obama mostly ignored the state. This time, it will probably be the other way around: Sanders will likely be visiting the state quite a bit, while Clinton will probably ignore it.
Also, something which merits mention, since someone brought up New Mexico: Even though Hillary did very well among Latinos in 2008 as well, she just barely won New Mexico (by about 1.1%.) Then again, she did much better in AZ this time around, so the same could be true for NM.