I dry fire as well, but the rule goes hand in hand with never aim at something you aren't willing to destroy. Even dry firing you should still be aware of your backdrop, you should still be aiming at a target, you shouldn't be pointing your gun at another human... IMHO (with the obvious exceptions of tactical training exercises). It's just easier to make it a mechanical part of handling your firearm than risk complacency in any scenario. Dry firing at home could be practiced at angles where a misplaced shot couldn't travel in to a neighbors house. It may not be possible in an active shooter scenario, but that's no reason not to practice it.
Well obviously even dry firing you don't go around pointing it at people you know are there. i'm not running drills where I draw down on people's heads dummy rounds or not. I'm just saying running drills inside a house, it is acceptable to point the firearm at the walls and run dry fire drills with dummy rounds whereas running any kind of drill with live ammo is not acceptable except in a shooting area or range.
The "tactical exercises" I personally when doing stuff like training for house clearing and the like I use a cheap 20 dollar airsoft gun that resembles my father's glock for that practice, and an inoperable crosman that resembles my model 10 for practice like that. a live firearm is NEVER used for tactical exercises at my house at least, I suppose I've never done the type of group training where muzzlesweeping your buddy is likely to happen though.
*I should clarify, real pistol is used for training for sight picture, practicing quick reloads, clearing stovepipes etc in a stationary way. drills involving moving through the house and checking rooms with drawn weapon are ran using toys and or props I own, that are CLEARLY marked as toys or props.