Semi-Autos not needed for self defense?

Why would the citizens of this country possible need to have these type of guns and that many rounds of ammunition? What viable purpose could they possibly serve? Remember the L.A Riots?

What do you do and how do you defend yourself when confronted with this kind of madness? Here is what you do.....

Granted, these type of incidents on a mass scale are rare. However, being attacked by multiple perpetrators in general is not rare. Having a semi-auto can help innocent people protect themselves & others against multiple attackers.