Wow... A condescending "young man?" Try to lay off the attitude to keep the discussion on topic and leave the ad hominem out of it.
First, any analogy that tries to compare prisons (filled 100% with criminals) to society as a whole is off to a weak start. Prisons and the general population of humanity are very different places.
And even then, your argument is weak.
Yes, there is crime in prison.
What impact do think allowing criminals free access to weapons in prison would have?
Obviously, prisons would be unsustainable with an armed population of prisoners and they would do whatever they wanted, including crime.
You illustration proves that controlling access to weapons does not stop crime 100%, which i agree with. However, it does nothing to show that controlling access to weapons does not PREVENT (your word) crimes. If prisoners access to weapons was not restricted, there would be more crimes in prisons. Well, at least until the prison was empty after all the inmates kill the guards and leave.
Given the topic of the thread, using logic, this is a good example. Ken's prison analogy does not logically support his claim, thus, it is a weak argument that should be avoided OR the claim modified.