When designing a game, at its core, almost every game is violent. Creation and destruction are the fundamental binary states of the universe. Of the two, destruction is the simpler to deal with. It has fewer states to define, even the animations are simpler to get looking right. Entropy is inevitable (well, until the guys and gals at CalTech get their butts in gear at any rate) and destruction, whether it be the removal of an obstacle or the crushing of a zombie corpse seems to be the simpler, and more universally understood process to follow.
I have students every turn who come to me with golden dreams of “non-violent” games, games that will be good for the world, that people will play because they are “good” and true and right. But sooner or later, that element of destruction comes into play. In order to progress you have to defeat an opponent, destroy a game piece, remove some sort of obstacle that stands in your way. So the social meme of violence, of a simple destructive solution is still there. They just removed the explosions and arterial spray. Is turning cute fuzzy creatures into bubbles any less destructive than unleasing the venerable BFG on a roomfull of imps? Not really. You’ve just substitued bubbles for smoke and fire. It’s an art-swap, not a fundamental change in the gameplay