By Brendan O'Brien

MILWAUKEE (Reuters) - David Clarke, the African-American sheriff of Milwaukee County, is a man on a mission - to rebut allegations that U.S. police have been too quick to use deadly force against blacks in a spate of killings from New York to Ferguson, Missouri.

The 38-year law enforcement veteran has become one of the most polarizing black critics of the "Black Lives Matter" movement that grew out of protests against the police killings of unarmed black men, which he describes as anomalies in an otherwise effective criminal justice system.

"My mission right now is defending cops. It's a full-time mission," the 59-year-old, cowboy hat-wearing, sheriff said during a recent interview. "I've got to defend this profession, because no one else is or very few are."

Clarke has taken on the national movement in appearances on Fox News and on Twitter, often calling the group "Black Lies Matter," and labeling its members "subhuman creeps" and calling for the movement's eradication "from American society." His stance has drawn the ire of black activists.

"If there was a white sheriff making those statements, they would have demanded his resignation by now," said Fred Royal, president of the Milwaukee chapter of the National Association for the Advancement of Colored People.

"His remarks have racist overtones to them. He's in total denial of the condition the average citizen in this community is being subjected to," Royal said.

Black Lives Matter contends black Americans are more likely to face violence at the hands of police than their white counterparts. A 2015 study by Britain's Guardian newspaper found that U.S. blacks were killed by police at a rate roughly 2.5 times higher than whites.

Clarke, who joined the Milwaukee Police Department as a patrol officer in 1978 and was appointed county sheriff in 2002, is unmoved by such criticism.

"It's not going to work with me," Clarke said. "I'm on the side of the law-abiding public. I'm on the side of victims of crime."

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CONNECTING WITH VOTERS

Clarke's tough-talking stance has resonated with voters both inside Milwaukee, one of the nation's poorest and most segregated cities, and in the more affluent suburbs, which have lower crime rates.

He has won four elections as sheriff with more than 70 percent of the vote in Milwaukee County, where 65 percent of the population is white. In the city, which is 39 percent black and 63 percent minority, he won 80 percent of the vote in 2014.

Clarke has run as a Democrat to the dismay of state Democratic leaders. He declined to say whether he was interested in running for higher office.

"The things that Sheriff Clarke says are not only truthful, but people are shocked to hear it come out of the mouth of a black man," said County Board Supervisor Deanna Alexander, a white supporter of Clarke.

Long before the Black Lives Matter movement rose to prominence, Clarke was known for admonishing residents of Milwaukee's inner city to take responsibility for their lives and take up arms to defend themselves against criminals.

"The heavy lifting has to be done by the individual and not government," Clarke said. "Government does not put enough pressure on people."

While Clarke has strong views regarding the residents of Milwaukee's inner city, his department does not have primary responsibility for policing their streets, a job performed by the city police department. The sheriff's department patrols highways, provides security at the airport and on county land and oversees the county jail system.

That fact is not lost on Clarke's rivals.

"Even though he tries to play one on TV, he is not a street cop," said Angela Walker, a Black Lives Matter member who is black and ran against him in 2014. "He's an administrator."

(Editing by Scott Malone, Ben Klayman and Peter Cooney)