You are comparing a fire extinguisher to a gun?
Here's my philosophy on things like guns and fire extinguishers.
Both are a way to mitigate a risk, in the case of a fire extinguisher, or smoke detector, we realize that while the risk of our house burning down is small, the consequences of such are huge. Obviously things like fire extinguishers, smoke detectors, seat belts cost money, time and inconvenience. But the cost is respectively very low compared to the consequence of not having them. In my opinion you'd be crazy to sleep in a house without smoke detectors, you'd be nuts to not keep a fire extinguisher near your garage and kitchen, and not wearing a seat belt is inexcusable. The risk so profoundly outweighs any negatives that these things are common place, lots of people feel the same way I do.
Guns for a lot of people are exactly the same. Some people see guns as a way that they can potentially mitigate risks to their well being. The rationale is no different than someone putting on a seat belt, or keeping a fire extinguisher near their stove. The likelihood of ever needing either one of those tools is probably extremely slim, but the consequences of NOT having them could be unacceptable.
On the inverse, a smoke detector costs almost nothing, and aside from the installation and maintenance time and cost there's almost no downsides. Guns cost more, in some cases a lot more, and carry a lot more responsibilities for their owners. Some people find the downsides outweigh the possible benefits, some think it's no different than putting on a seat belt. Neither one of those people is wrong.
We all do thousands of risk/reward calculations every day. Some people don't value smoke detectors. Some people don't value guns.
Trying to convince someone that their calculation is wrong is probably going to be futile, I've been trying to get my dad to wear a seat belt for 30+ years. He's spent almost 70 years not wearing them, to him they have no value and only bring downsides, to me they have no downsides and only mitigate risk.
If you don't like the idea of people carrying firearms in their Teslas that's your prerogative. You can not partake in the activity, live in a place it's not allowed, you can vote in politicians that align with your thoughts and you can push for laws to make the practice illegal. What you cannot do is understand fully why someone's risk/reward calculation came up differently than your own.