As Lilith had explained to Bai Zemin several weeks ago, Soul Stones were not to be consumed by any means.
Although Soul Stones could grant the soul evolver of any race a great power boost depending on the quality of the Soul Stone consumed, the risk was too high. Since the mana contained within the Soul Stones was mana that could not be controlled by the fleshly body, the soul would suffer the consequences while trying to withstand the assault of foreign mana and therefore at best the soul would end up damaged; which would consequently weaken the soul evolver for a period of time corresponding to the severity of the damage the soul received during the process of assimilation and consumption of the Soul Stone.
Then, after knowing all this one could try to imagine the shock that Bai Zemin felt when he witnessed with his own eyes how the existence in front of him consumed a Soul Stone as if he was eating a candy.