When it endangers the species, the environment, or dangerous for people. Just when it's not safe in general.
Because We've been genetically modifying our species civilization to avail in all creatures to deciding to gathered wild and plant them behind his lean to cave.
Never! We've been genetically modifying plants and animals since the first guy decided to gather wild seeds and plant them behind his lean to or cave.
People today, at least in our progressive, affluent western nations, are so far removed from real agriculture and so ignorant regarding food production, that they're nearly child like in their perceptions and demands about the food they consume. Most people have just enough information to be dangerous to themselves and the people they influence.