Yesterday's "Gun Safety Forum" in Las Vegas featured a lot of emoting, a lot of sympathizing with victims of gun violence, and a lot of praise for young activists pushing new restrictions on firearms. But judging from the four interviews with Democratic presidential contenders that I watched, there was little in the way of policy substance. The absence of thoughtful, evidence-based arguments in favor of "common-sense gun laws" was especially striking because each candidate had half an hour to defend his or her views. Instead they simply asserted the need for the mostly indistinguishable policies they favor while perpetuating several misconceptions that continue to cloud the debate about gun policy. Here are the most striking examples:

1. Gun violence is an "epidemic."

Former Rep. Beto O'Rourke (D–Texas) promised he would "end this epidemic in America," Sen. Kamala Harris (D–Calif.) agreed that "we have an epidemic," and entrepreneur Andrew Yang said, "This is clearly a public health epidemic." Of the four candidates whose interviews I watched, only Sen. Amy Klobuchar (D–Minn.) failed to invoke the e-word.

While it's true that firearm homicides rose between 2014 and 2016, they fell in 2017 and again last year. Furthermore, the firearm homicide rate is still far below its peak in 1993. The total homicide rate last year was half the rate in 1980.

2. In light of the risks that students face, mass shooter drills in schools are sadly necessary.

The interviewer, MSNBC anchor Craig Melvin, noted a couple of times that his 5-year-old son had recently undergone a "lockdown drill" at school. Melvin worried about "rear[ing] an entire generation of kids who are constantly living in fear of being shot."

Klobuchar, who is 59, noted that she never had such drills in school when she was a girl (when the homicide rate was actually higher than it is now). "The solution is that we need to greatly reduce gun violence," she said, in which case "maybe you won't need to have these kinds of education drills."

Harris likewise accepted the premise that mass shooter drills make sense. "I have always thought about this issue…through the eyes of a child," she said. "Our children—elementary, middle, high school students…over the course of the last few weeks have been going back to school to endure a drill where they are taught about how to hide in a closet if there is a mass shooter roaming the hallways of their school….This is traumatizing. Our children…should be sitting in a classroom and opening their mind to the wonders of math and art and science….Instead half their brain is concerned, legitimately, about a mass shooter busting through the door."

Only Yang, to his credit, argued that the fear and anxiety such exercises instill among children and parents cannot be justified by any plausible safety payoff. "We're undertaking these activities," he said, and "it gives rise to a real sense of uncertainty for the child. If you can't be secure in your own classroom…your entire sense of the world gets shaken….If you have that certain cost and a very uncertain, speculative benefit, you have to give your kids a chance to go to school and not worry about getting shot."

Given the infinitesimal risk that any given child will be threatened by a gunman at school during the 13 years from kindergarten through 12th grade, Yang is surely right. Yet gun control advocates like Harris routinely hype that minuscule danger to advance their agendas.

3. "Assault weapons" are uniquely deadly.

The entire Democratic field shares that erroneous view, arguing that firearms with certain "military-style" features have no place in a civilized society because they are designed to kill many people quickly.

O'Rourke, who wants to ban and confiscate "assault weapons," reiterated his claim that such guns are distinguished by the destructive power of the rounds they fire. Klobuchar, who wants to ban "assault weapons" and institute a voluntary buyback program, called them "killing machines," a term that could accurately be applied to any firearm. Yang, who favors a tiered gun licensing system that would impose restrictions based on the potential threat to public safety posed by each class of firearms, thinks "assault weapons" are manifestly too dangerous to be tolerated.

"An assault weapon was designed to kill a lot of human beings quickly," Harris said. "It's the design of the thing. There is no legitimate reason or purpose for them to be on the streets of a civil society."

Contrary to those claims, the characteristics that distinguish "assault weapons" from other firearms—features like folding stocks, barrel shrouds, and pistol grips—have nothing to do with bullet size, ammunition capacity, rate of fire, or muzzle velocity. And while Klobuchar described military-style rifles as "the mass shooting weapons," most perpetrators of such crimes use handguns.

4. Background checks are an effective way to prevent mass shootings.

All of the Democratic contenders think background checks should be required for all gun sales, including those that do not currently involve federally licensed dealers. Klobuchar argued that mass shootings have increased support for that policy.

Yet the vast majority of mass shooters do not have disqualifying criminal or psychiatric records, making background checks irrelevant in those cases. Even when mass shooters are legally disqualified from owning guns, it is debatable whether they would be deterred after unsuccessfully trying to buy firearms from licensed dealers, as opposed to obtaining them through private sales that the government could not monitor even if background checks were notionally "universal."

It makes little sense to expand background checks in response to mass shootings they could not possibly have prevented. But Klobuchar said pointing this out is "just excuses," because "we know that not one size fits all" and "there are a lot of different solutions."

5. The Second Amendment is all about hunting.

"I come from a state…with a proud hunting tradition, and we've got to remember that there's a lot of law-abiding gun owners out there," Klobuchar said. "I look at these [gun control proposals], and I say, 'Does this hurt my Uncle Dick in his deer stand?'"

We have met Klobuchar's Uncle Dick before, and he still is not an exemplar of all the rights the Second Amendment is supposed to protect. A ban on all handguns, for instance, would not stop Uncle Dick from shooting deer, but it would nevertheless be unconstitutional, since it would interfere with what the Supreme Court has called "the core lawful purpose of self-defense."

O'Rourke did mention self-defense as a legitimate reason to own a gun, but he also argued that an AR-15 is clearly not covered by the Second Amendment because people "don't need this to hunt." He also seemed to question whether any modern guns are covered by the Second Amendment, noting that they fire faster than muskets did. The Supreme Court has explicitly and repeatedly rejected the idea that the right to armed self-defense extends only to weapons that were available when the Second Amendment was written.

Harris agreed that the right to own an AR-15 is not protected by the Constitution, even though such rifles are "in common use" for "lawful purposes," the test prescribed by the Supreme Court. "You can respect the the traditions of hunting among families in our country," she said, and still support an "assault weapon" ban.

Harris also repeated a puzzling formulation of the issue that suggests she has not given much thought to the restrictions that the Second Amendment imposes on gun control. "I'm not going to any longer accept your false choice that you're either in favor of the Second Amendment or you want to take everyone's guns away," she said, implying that you can be in favor of the Second Amendment and still want to take everyone's guns away.

Like O'Rourke, Harris was hazy on how far politicians can go without violating the Second Amendment. The Constitution is "a living document," she said, and "its principles must be applied to the realities of today."