I think the reason that people are troubled is that this apparent exaggeration makes us wonder what other aspects of the story are also exaggerated.
If I read your story correctly, your son and two African-American friends were reported to the police as suspicious for no reason whatsoever. The primary cause for the report appears to be that your son's friends were African-American and therefore should be investigated.
However, African-Americans make up approximately 25 percent of Oakland’s population. If simply walking down the street while black results in 12 police cars being called out and neighbors questioned, then Oakland must have thousands and thousands of police officers standing by to investigate so many African-American pedestrians.
Oakland is well-known for having a very high crime rate. http://www.sfchronicle.com/bayarea/johnson/article/Oakland-s-unspoken-good-news-homicide-rate-6913876.php
Therefore, it doesn’t make sense that police would have nothing else to do than send out a dozen cars to investigate a report of a potential burglary.