Don't get it. The logic of that is people would be as well of with single shot pistols. That sort of flies in the face of firearms development over the last few hundred years. Rate of fire and ability to fire the most bullets without reloading.
That's kind of taking it to extremes. The argument is more of if 6,7, or 8 rounds aren't enough you are probably in more trouble than 15 or 20 will get you out of.
Of course there are always exceptions, however rare, but as a rule most SD shootings are one or two rounds at very close range. Even in the event that more are needed, if it's more than 10 there is really