politically correct mainstream media
I'm sure most have noticed that the mainstream network media (NBC, MSNBC, CNN, etc.) have given very little coverage of this relatively new phenomenon in mob mentality. FOX was the first to cover and reported it as it actually was; mostly young black males gone wild.
Some instances where white people were targeted for violence by blacks,(see Wisc. State Fair), the authorities danced around the subject and refused to call it like it is and label it as a hate crime, black on white. Reverse this situation and show a mob of white youths beating blacks while yelling racial slurs and Brian Williams would be doing his NBC Nightly News from the scene, competing with other mainstream media to get first hand accounts from victims.
Many well thought out responses to the OP's question here on this thread. I try to be as rational and level headed as I can be and will go out of my way to avoid confrontation, call 911 when appropriate, be a good witness and such. But I'm in the camp of those who can't stand by and watch an innocent person be beaten or worse. Of course, there are variables to consider, but if I'm on my own with no loved ones present, you may be reading about me in the news or see me on a flash mob video...