You didn't reply to my last post where I explicitly asked questions.
Anyway, no that's not the case. The argument of "well only law-abiding-citizens are effected by gun laws because criminals will break the law!!" is utter trash. The current system for firearm ownership allows for a massive black market trade; if the ability to purchase guns was limited, the guns on the market would be further limited, with the black market trade following. I myself would suggest a buy-back program, but lets ignore that.
Your average Joe who commits a mass shooting his just that, your average Joe. We can make arguments about their mental stability all-day-long, but an overwhelming majority of firearms used in mass shootings (I believe 89%, but that's off memory so don't hold me to it, it may be higher) are bought legally. These averages Joes - and they are average Joes albeit with whatever issues - are purchasing guns from their local gun stores. Can't purchase it from there? Well, shit. Navigating the black market isn't exactly easy, it isn't a location with some stalls and without some type of connection, (arguably) mentally unstable people are going to have a real problem getting their hands on guns. While not identical, such a scenario can be examined in the ease of access in countries such as Australia and the U.S. If you did have the connections to buy a high powered semi-automatic rifle illegally, the cost difference is astronomical. Your average 22 year old white male in all likelihood will not have thousands of dollars to drop on an AR-15 (opposed to $700). Ok, so what? They use pistols for their shooting spree instead? Well, we could implement laws to help prevent this, but let us say we don't. Pistols will in all likelihood be just a little bit less effective than a military-style rifle both in ammunition capacity, accuracy, and stopping power. Effectively saving lives.
"Guns removed from the world.. impact would be minimal." Again, no. Guns are chosen yes because they are there, but also due to how effective they are. You are much less likely to survive a suicide attempt via firearm than you are via pills. I would argue - and I am sure there are a variety of papers that do just that - that if guns are not in the household, there is a significantly higher chance of surviving a suicide attempt; therefore, a higher chance of getting past whatever is troubling the individual.
You make it sound so easy to steal a gun or buy a gun off the black market. Hmm.. let me go steal an AR-15.. well first I need to figure out where/who to steal it from, than devise a way to do it, then ensure I don't get caught, and then plan my attack. Even if it was easy, it would be an extra step - where someone could very well get caught - to committing a mass shooting and I do not see the problem with that.
Want to site a source or at least some statistics for your gang violence claim? What is nearly all? 90%? 51%?
To the contrary, classes will require responsible owners to purchase the weapons and common sense would hint that common owners not auctioning off their guns to the highest bidder... Safety classes would ensure individuals who own a gun know how to use it (God forbid). I'm not going to really try and make the argument it'll limit gun use in gangs and other similar situations, but that's why there could be other laws.. like hmm a universal back ground check, or perhaps limiting semi-automatic weapon ownership, or providing justification for owning certain firearms, or a variety of other possibilities.
Edit:
And responsible gun owners would be unaffected. Responsible gun owner? Awesome! You'll have no problem passing a mental health examination and a gun safety course. Sorry you had to set aside a few hours of your weekend to ensure you don't go slaughter individuals!