"It's inherently racist because, number one, it divides us. ... All lives matter: White lives, black lives, all lives," he told Fox News on Monday. "Number two: Black Lives Matter never protests when every 14 hours somebody is killed in Chicago, probably 70-80% of the time (by) a black person. Where are they then? Where are they when a young black child is killed?"
Giuliani told CBS on Sunday that he thinks the activist movement, aimed at preventing violence toward the African-American community, exacerbated racial tensions by putting a target on the backs of police officers.
His comments came in the aftermath of the shooting of Dallas police officers last week, in which gunman Micah Johnson targeted officers patrolling a non-violent Black Lives Matter march against the deaths of Alton Sterling and Philando Castile at the hands of law enforcement.
Giuliani also defended himself against criticism that he did not appreciate the problems faced by the black community, standing by his record as mayor of New York City from 1994 to 2001.
"That ain't the truth. The truth is, number one...I prosecuted more police officers than any other mayor in New York history," Giuliani told Fox. "I put 70 police officers in jail... I am perfectly capable of understanding when police officers act improperly and they should be made an example of when they do."
Giuliani said he understood why some people in the black community did not trust the police, but he hopes that would change.
"I would like people to know that the New York City Police Department is a non-majority white police department," Giuliani said. "I understand the other side of it. I don't mean not to talk about the other side of it ... The American people get a wrong impression and Black Lives Matter, therefore, puts a target on the backs of (police officers)."
Black Lives Matter co-founder Alicia Garza on Monday called Giuliani's comments "a relic of the past."
"What those comments show me is that the former mayor doesn't understand racism," Garza told CNN's Don Lemon, adding that his comments were "not rooted in fact."
She noted that if former House Speaker Newt Gingrich can acknowledge the reality racism, she does not understand "what's stopping the former mayor."
"Racism is a system -- it's not about people being mean to each other," Garza told Lemon. "So when we have a system that has black people at the losing end of every single disparity that you can think of, that's what racism is, and that's how we know that the former mayor doesn't really know what racism is."
Texan congresswoman Sheila Jackson Lee, who introduced the Law Enforcement and Integrity Act in 2015, dismissed claims that black families were to blame for the community's strained relationship with law enforcement.
"I'm a mother of an African-American son and I teach my son at all times to respect authority," Rep. Jackson Lee told MSNBC. "Mayor Giuliani, I want you to understand the predicament that African-American families are in where there is the very thought that sending their sons out into the world... that they won't get the same treatment under law."