Some good points Madmorbius.
There is a big difference between model planes, boats, and replica firearms. The main difference being that replica firearms have potential for severely harming society while model planes/boat forseeably at the moment do not.
Now here me out on this. In a crime, if you remove the tool, yes, the intent is still there, and you have not fixed the basis of the problem. The criminal may even simply pursue a different tool (knife, finger) to commit the crime. However, firearms raise the severity of a crime. Firearms are on the extreme end of lethal weapons. They have the range to harm all those in vicinity of the area as opposed to samurai swords and Ka-bars. A man holding up a store with a replica firearm or real firearm is much more dangerous to the eyes of society, especially police, than one using a knife. Replica firearms increase the number of times a police officer is forced to encounter (in their eyes) a lethally armed criminal (real of fake gun). A politician will easily outweigh the needs for replica firearms - a police officer having to deal with a potential life or death situation or a few people getting to roleplay more accurately.
You covered an interesting area in your post MadMorbius
Why do we react differently when some idiot uses a toy gun in the commission of a crime? Just as the drunk driver is responsible for driving drunk, a criminal is responsible for pulling the trigger. Likewise, when a criminal brandishes a toy weapon to a police officer and winds up dead, we should not blame the availability of the toy or the officer's reaction. The criminal made a concious descision to put themselves at risk, and as such the criminal is directly responsible for the outcome.
That is a very honorable and simple way to view life, however life is not black and white. Take this for example, if every single citizen was armed with a firearm, do you think crime would increase? With your rational, it would not, since a tool does not create a criminal. If every drunk individual in a bar possessed a hidden knife, would there be more stabbings? If every Canadian was provided a cigarette, would not more people smoke? Putting full responsbility on the individual is respectable, however it is not realistic. Accessibility is a huge factor - it can create a crime. Many crimes can be situational. I've witnessed fights where someone in a crazy drunken rage has attempted to use whatever objects around them as a weapon. The severity of his crime was directly related to the effectiveness of the weapon he could get his hands on. He screamed to the other fighter that he's lucky he left his knife at home. That night, poor accessibility saved the other man's life. That altercation ended there, and nothing ever came from it.
Providing easy access to replica firearms does create crime as well as unnecessarily raising the severity of the crime.