Bullshit. How do you know that you don't know anyone that was affected by it? Do you know which week in 2012 the experiment was conducted? Do you know which of the ~billion FB accounts were the 700k experimented upon? I find it pretty shocking that so many people are having difficulty understanding the difference between A/B testing and intentional emotional manipulation where a significant negative (or positive) result was the data point the study strove to measure.
I can quite imagine that a significant number of offline lives were impacted by this experiment. People exposed to negative content presumably don't limit their negative reactions to behavior only in the venue where they were exposed to the negative content.