I suggest you read the source again because the overall data shows the following: "Do gun control laws reduce violence? To answer this question, a city-level cross-sectional analysis was performed on data pertaining to every U.S. city with a population of at least 25,000 in 1990 (n = 1,078), assessing the impact of 19 major types of gun control laws, and controlling for gun ownership levels and numerous other possible confounders. Models were estimated using instrumental variables (IVs) regression to address endogeneity of gun levels due to reverse causality. Results indicate that gun control laws generally show no evidence of effects on crime rates, possibly because gun levels do not have a net positive effect on violence rates."
There are a few exceptions to this that include addicts, criminals, and the mentally ill.
"Weaker evidence suggests that bans on gun purchases by criminals and on possession by mentally ill persons may reduce assault rates, and that bans on gun purchase by criminals may also reduce robbery rates."
It should not be suprising that this small demographic would be more prone to violence.
Obama, Biden, and Democrats do not just want to limit guns to these demographics, but to everyone. After all, it is already illegal for felons and the mentally ill to be given a gun.
I'm not against all gun laws; I think that the mentally ill should not be able to get guns nor should felons. But limiting it to the general population when severely limit DGUs and be unconstitutional.