Does a fire extinguisher guarantee you can protect your home from a fire? No, but it gives you a fighting chance. And a fire extinguisher in your car means you may be able to help someone else.
Guns in the hands of peaceful people are no more dangerous than fire extinguishers, and just serve as a tool that may help in another kind of emergency.
And before someone says, "But fire extinguishers aren't lethal," my gun isn't either unless you try to harm me or those around me. Why do you think people call cops in an emergency? Because they have guns! I won't be butting in on your peaceful life because of puritanical busybody bullshit. I am safer than a cop.