Whether it'd be in the constitution or not wouldn't have mattered a single bit.
The mere fact that guns exist means they'll be misused (in the broadest sense of the word, since it's designed to incapacitate/kill), and that is something that won't or even can't be changed.
I disagree. Of course now that guns exist there will always be some around but different laws can still change the situation A LOT. For example take a look at the different situation in Germany compared to the US.
In the US every hoodrat/ghetto thug has a gun and a lot of them carry them around. When the police stops a car they draw their guns, most police officiers will make use of their gun probably more than once during their carreer, in some areas even on a regular base.
In Germany on the other hand were owning a gun is a certain prison sentence it's very different. The only criminals who own guns are almost always organized crime and those rarely use it on regular people.
The common thug here in Germany simply does not need a gun since the people he is dealing with are not armed either. Hell even most knifes, batons etc. are illegal to own, yet alone carry around. You can go to the areas that are considered really tough and "ghetto" here in Germany and still barely no one carries a gun because the risk is too damn high.
I come from a big city that is considered a social hot spot with high crime rates and the main scene for the feud between Hells Angels and Bandidos and yet shootings are almost unheard of. A shooting might happen once a year or every other year and then it's a high possibility that organized crime was behind it. 99% of the police officers will never ever use their gun during their whole carreer, most will probably not even draw it.
So don't say the situation can't be changed because it can be changed. It's the law that makes it change and not the availability of guns since that's pretty much the same anywhere in the world .. if you want a gun you can get one, same with drugs or most other illegal stuff.