CNN host Soledad O'Brien on Thursday scolded Sen. Chuck Grassley (R-IA) and told him he should know better than to try to link assault weapons to "black violence on blacks" because most recent mass killings had been carried out by white men.

Following National Rifle Association chief Wayne LaPierre's Wednesday testimony to the Senate Judiciary Committee that he opposed universal background checks at gun shows, O'Brien asked Grassley why not support something that seemed like an obvious part of the solution.

Grassley argued that universal background checks would burden people trying to buy a gun on Sunday.

"Obviously we have some background checks, it's how encompassing do you do it?" he explained. "Do you do it for one father selling to a son or another relative or how do you cover everything? I think that's the issue. And also, the extent to which you have private sales on Sunday between relatives, and maybe you can't access the system all the time and as fast as you want to do it."

O'Brien pressed Grassley on why he opposed an assault weapons ban, when even the temporary 1994 ban had reduced the number of crimes involving those firearms by between 17 percent and 72 percent, according to a 2004 study by the University of Pennsylvania.

"I guess you can argue over numbers," Grassley replied, adding that the Columbine High School massacre had occurred during the 1994 ban.

"Part of the argument is if you start now that there's potential down the road to make some of a difference," the CNN host pointed out. "Sometimes I hear the argument that you're never going to get rid of all the guns or you're never going to get rid of all the assault weapons. It seems to me to be a little bit of a specious argument."

O'Brien then wondered why Grassley was also against a "common-sense kind of thing" like tasking the Center for Disease Control with studying gun violence.

"The Center for Disease Control is all about studying diseases, and ownership of guns is not a disease," Grassley insisted.

"Public health?" O'Brien noted. "If you look at a city like Chicago, where there has been just massive, massive deaths from gun violence. That's not a public health issue?"

"Well, I think that's the place in our society where you would study the issue of black violence on blacks," the Iowa Republican asserted. "Most of those guns are pistols and not the guns that you're talking about on this program."

"Well, certainly when we are looking at assault weapons, I know that you know that most of the perpetrators have been white men," O'Brien remarked while noting that the CDC had spent $2.5 million studying gun violence in 1993.

"I would think that anybody who wants to figure out how to stop people from dying in gun violence -- whether it's suicide, whether it's small children being killed in a massacre, whether it's domestic violence -- that just studying the issue would be a good idea for everybody," she continued.

"I said I agree with you because that's part of the mental health issue that we have to deal with, yet, during this debate," Grassley replied. "Because in everyone of these instances that keeps cropping up, where mass killings, people had mental health issues. They shouldn't have had guns in the first place."

Watch this video from CNN's Starting Point, broadcast Jan. 31, 2013.