It's not cannibalism... it's more like if there were other species' that human could communicate with and had similar level of intelligence, able to befriend them, etc, aaand we eat them. Surely that would cause some guilt, eh? Or let us put it this way. Imagine eating your pet dog or cat that's...
I have a feeling that "THAT" might be something related to the king. Perhaps all this 'farce' Rose did was actually orchestrated by the king in order to push bad bugs (eg. Liliana) from getting close to the prince and firmly put Rose's position as future queen? What do you guys think?