If I understand correctly... :
Your 1D texture has 4 components (4d vector). ( desc.Format = DXGI_FORMAT_R8G8B8A8_UNORM; -> R,G,B,A)
If you sample at location 0 it will read the 4D vector. That 4d seems to be (1,0,1,0) (R and G are 1).
RGB components are not separated, they are combined.
So when you mixed them you get purple.
You need sampleLevel(sampler,0,....).x to get red.
SampleLevel should be used if you need a specific mip-map, it has nothing to do with RGB channels.
EDIT: you should use the default sample function, not sampleLevel if you don't need mip-maps.