Every now and again, though, you wind up with a product like that ridiculous sightless "Boomer" from Charter Arms that really is a "belly gun". As a result of doing a lot of shooting for work, I can index shoot (ie, with no more of a sight picture than having the gun up in my field of vision in a firing grip) pretty okay. I could probably keep them all in the 8 ring of a B27 out to maybe as much as ten yards with no actual sights on the gun.
Thing is, not every civilian defensive gun use situation is a "keep them all in the 8-ring" sort of problem. Just ask that retired officer working as a security guard at the Buffalo grocery store.
Now, I'm on record as saying that unless an active shooter situation pops off right in my lap, my Plan A is to head toward whatever the closest exit is that's away from the sound of the gunfire.
But if you think you want to get yourself involved in that situation, you need to ask yourself if you have the ability and the means to do so, and the time to think about that is before someone's busting caps two aisles over in the Piggly Wiggly.