A fire extinguisher is easy and intuitive to use correctly. A gun requires extensive training — spending large portions of my life thinking about and practicing how to kill a fellow human.
The fire is not going to wrench the fire extinguisher from my hands and use it against me. A burglar might well do so with a gun.
If a young child stumbles across my fire extinguisher out in the open, no harm will ensue. If he comes across a gun… well, we all know the stories. (And if your guns are safely locked away, you won’t be able to access them quickly enough to do you any good in a breaking-and-entering scenario.)
There are many ways the analogy breaks down. Ultimately, though, it comes down to, am I willing to live with having taken a life — in the most dangerous neighborhood I ever lived in, it would likely have been a teenager’s life — in order to defend, at most, a few thousand dollars of material possessions in my home? If I’m not, I have no business with a gun. And I’m not.