As he looked across a room filled with civil rights veterans, White House officials and leaders from corporate America, Martin Luther King III said that the issues his father championed and died for have yet to be fulfilled in many communities across the country.

“My heart is heavy today! A people who do not remember their history are doomed to repeat their mistakes,” said King, who spoke at a luncheon in the District, sponsored by the National Action Network, that was held on what would have been his father’s 84th birthday.

The Rev. Al Sharpton, the group’s president, hosted events in Washington and New York on Tuesday in honor of the slain civil rights leader, but he told community leaders to beware of reducing King’s legacy to the commemorative events held around his birthday.

“Martin Luther King can’t be reduced to a ceremony,” Sharpton said....