For lack of a better term, corpse yin qi was considered impure or tainted yin qi, and rightfully so, given the effects it had. To use it was to defile oneself and others.
It had long been hypothesized that corpse yin qi was the amalgamation of all the negative energies of the deceased—their obsessions, frustrations, regrets, bitterness, anger, wrath, hatred, fear, and any other powerful negative emotions they held at the time of death. To absorb the corpse yin qi they produced was to take in those very emotions.
This was assumed to be one of the guiding reasons behind the unstable, bloodthirsty, and irascible nature of cultivators who used corpse qi, and why they were attacked on sight. They were regarded as no different from the toxic miasma produced by concentrated corpse yin qi.
Death yin qi, however, carried no such stigma.
