Gun control is never an easy issue to work with, especially since the United States is one of the leading arms manufacturers of the world (see the movie Lord of War, with Nick Cage, for more details). And that especially counts double when you toss in the usual battery of untruths that people do in the debate to make their side the winner.
People who are against gun control are for more mass shootings and dead kids - which I can assure you, outside of a handful of psychopaths, nobody is. Everyone is against Sandy Hook and Columbine and Jonesboro; the people who say that there aren't are being dishonest and trying to taint the debate with accusations of inhumanity so as to invalidate the opinions of others.
The government is coming to take all your guns - they're not; regardless of your interpretation of the 2nd Amendment, I doubt very much that the police or whatever authority would be used to come and 'take these guns' would. Primarily because...well, if you had a choice between going and taking the guns, and potentially getting shot (or shot at), or leaving them alone, and the person in question was someone who had caused no prior problems, what would you do?
The debate surrounding gun control today primarily revolves around the ounce/pound prevention/curative maxim - that's why we see things like background checks and waiting periods, regulations that surround getting carry permits, and weapon/accessory bans. Cut it off at the source, rather than after the fact. The usual reply to this is all that does is prevent or burden people who want to legally own firearms, and won't stop criminals who will buy them off the black market. This is technically correct - if you are planning on illegally acquiring one, then it doesn't matter how many different gun regulations are in place, what you are doing is bypassing all of them.
But back to Bernie and his stance on guns. He's absolutely right. We don't allow people to sue the beer companies or the car manufacturers when a drunk driver runs them over in the street, because we recognize that people have agency - they chose to get drunk, and then they chose to drive. The fact that they had 12 Pabst Blue Ribbons and hopped in their 95 F-150 to drive home has nothing to do with the fact. They could have had 6 triple shots of tequila and been driving a 2014 Lincoln; the constant is the driver and their actions.
That said - we do hold companies to a standard. The bog-standard of this is the Ford Pinto - the company knew it had designed an unsafe car, and took no steps to address the concern, or even warn the public, because a cost-benefit analysis indicated it would be an easier financial burden for the company to simply pay off any lawsuits than fix the car. Gun makers need to be held to a similar standard; this is tricky, though, because of the difference in product. Cars are supposed to be safe to drive on the road, and abide by certain regulations. But firearms are always dangerous. Figuring out where to set the bar isn't a slam-dunk, but there should be a bar.
As a side note, I think Bernie did a lot better at that debate than Hillary did, because Bernie made hay of the thing that needed to be said over and over again - her political corruption. Have him add that to his usual stances on most issues, and I personally think he'll be unstoppable.