But you shouldn't defend yourself. That is the job of the police and that's why they should have them.
Ex-CUSE me!? ... *Deep breath*
Okay, well, let's go over a few things.
1. Where did the police begin? As local militias. Normal people gathered their own weapons and organized to defend their towns. Then, people organized further and paid a few to guard the town full time. The police are normal people who are given weapons and supplies. By us, for us. How are they anything less than normal people?
2. I WANT to defend myself. The police can help, sure. Let them. I welcome their assistance. It doesn't mean I shouldn't be allowed to defend myself. If you rely on the police, an alarm, a dog... You're relying on someone else to defend YOU. I would much rather be allowed to defend myself. Sure, if I can, I'll let the police handle it, but if my life is in imminent danger, 911 isn't really going to help that much...
3. If we shouldn't defend ourselves, then the whole basis for the police evaporates. You can't really say "You shouldn't defend yourself" and then say that the police have the job to do so because the police were created as an attempt at self-defense. They are inherently flawed to a degree in that respect, but that's why they came to be.
For a start they are trained to use them.
And that makes them less susceptible to kill people... How? A part of licensing is that you have to undergo simple training. A part of CCP's, in some places, is learning to shoot and carry safely in public, and the gun club my family visits regularly runs training courses akin to police training. In fact, many members have run training courses FOR the police. We license people to use cars because we know they're at least marginally capable with them and more people are killed by cars than anything else. That's why I'm okay with gun licensing; because you're letting competent people get what they need to protect themselves.
And otherwise you would just end up with militias.
The police are a militia. They're a militia being paid full time. They are ordinary people who have taken up arms to defend the populace. They are more regulated and regimented, but it doesn't make them stop being militia.
Seriously, if you put the law into citizens' hands then, well it wouldn't be good
Well, the law IS in our hands, but that's not what I want so much as being able to defend oneself.
Edit: As to Yokto's statement, it used to be, in Western society when swords were still about, you carried a sword everywhere. The sword was also your table knife and multi-tool. It was used for everything but it was created, first and foremost, as a weapon. This was in the days long before the fork came about, really. Since guns have arisen, swords have declined, though, and so has the usage of knives as a killing tool.