"But in the long run, is it really doing anyone a service to pretend that there is a "one step" answer that will work, when evidence indicates -- over and over -- that it isn't one factor but many that result in this kind of evil and the resulting suffering? "
1. Neither Obama nor anyone else has suggested that there is a "one step" answer.
2. Of course there are many factors and nothing we can do will completely eliminate this kind of event from happening.
3. If there are many factors to take into consideration and the goal is to minimize the occurrence of tragedies and also minimize the casualties when tragedies do occur, then you do have to take at least a first step (followed by other steps) when trying to solve a serious problem.