There's a difference between a group riding recklessly and feeling intimidated by that environment (from which you can likely just slow down and disengage -- because if they are "riding" recklessly they just keep on going) and being surrounded by and directly aggressed against by a horde.
If the latter I don't care if they're on foot, on tricycles or on Suzukis. That grandkid you pose as example isn't more important to you than any one of the group that is your perceived threatening mob? If you think the threat is real you get the hell out if you can. "Kill them all and let God sort it out" may not be PC; but the sentiment has a place.
Well certainly I would take whatever action I found necessary to protect my family & in fact would do the same for my friends. Some of these friends at times act about the same as my young grandchild, but I digress.
As to options of the driver of an SUV surrounded by an angry horde of crazed bike riders - one has several options. One is to call 911 & wait. Another is to attempt to find an escape route that does not physically harm anyone or any property. Another option is to floor it & run the hell over anything & everything that is in the way. Another is to get out of the SUV & try to reason (not advisable), and yet another is to attempt to defend oneself in an event that is required. Still another is to get pulled out of the SUV & have the living hell beat out of you.
VaEagle outlines some interesting likely future events that may sort this out, but in all likelihood there will be truth, lies, not the truth, almost the truth but not quite, and sheer fantasy - with a slice of each for any who wish to partake. Such is life in our court systems.
Killing them all & letting God sort them out in this case is a little bit extreme, but then again the world could be a better place for it. Am hopeful when on my future rides that some cager fellow does not fear for his life when he sees a horde of Harleys on their way to some local eating establishment or purveyor of frosty beverages and decide to take a few of us out. Probably will not happen, considering.