Archangel has it right.
There is a continuum for civilians.
- Being there, or not being there, can be enough to address some problems.
Just walking away is often enough. Showing up can also cause the perp to reconsider an action, esp. against someone else.
- Verbal deterrents can work. Making your intentions clear can make a perp reconsider.
- Lightly removing contact may be enough. They touch/grab you, proper application of body mechanics can remove them. This can, again, cause them to reconsider.
- Pain compliance escalates your response, but without serious consequences. OC, Kubaton, pressure points, etc. induce involuntary reaction in the perp's body, permitting you to redirect/restrain him, and persuade him that maybe what he's doing really isn't good for his well-being - there is a price, and continuation better be worth it for him (likely isn't).
- Physical damage makes him unable to continue the assault, but is survivable. Remember: you're not out to kill him, you just want him to stop harming/threatening you. If, after breaking an arm or wrenching a knee, he will be unable to continue harm, then do so and stop there. Muggings, bar-room brawls, etc. mostly fit here.
- Lethal force. Someone is gonna die, you're just re-arranging who. Any lesser response means your attacker continues to have the opportunity, ability, and intent to kill you (you may break his leg, but he can still shoot you).
It's ridiculous to expect an untrained and unequipped person to follow a force continuum.
Regardless of your training & equipment, you WILL be legally held to a continuum.
If some guy starts shoving you around in a bar, you don't shoot him - you disengage and/or use pain compliance.
If some guy approaches your wife in a suspicious manner and your spidey-sense tingles while she's well ahead of you in the parking lot, you don't take the 50-foot shot - you catch up and inject your physical presence, or verbally tell him off.
If you hear glass break at oh-dark-thirty, and while going down the stairs to investigate you meet up with a stranger holding a crowbar, you don't politely ask him to leave - you apply Gaston's point-and-click interface.
This is why, ideally, along with my G26 I have an ASP, Benchmade, and Kubotan. Most hostile interactions are _not_ going to require lethal combat, but will call for something lesser.
All that said, I'll agree that the continuum for police and civilians (and soldiers) are different. This is why Ayoob and Cooper came up with different color codes. Police have the equipment and infrastructure and motivation to delay transition into lethal force, and have justification to go into lethal force more readily. Civilians have justification to go into lethal force sooner, but for fewer reasons.