I will agree that both of these groups (ADL and SPLC) are, today, smear outfits.
I don’t know that SPLC ever had any legitimacy.
There is no controversy that ADL was formed to clear the name of Leo Frank, who was viewed by many as having been wrongfully convicted of murder because of his Jewishness. The organization went on to fight many forms of discrimination against Jews.
But, in recent years, ADL has simply joined into the Democratic agenda in terms of demonizing those who have opinions it disagrees with. This makes ADL, as you say, a racist organization. Smearing entire groups of people for the evil of fringe-types within those groups is a denial of the reality of the human condition, is hateful, and justifies, if not incites violence.
The ADL and, for that matter, the ACLU have lost touch with their past. They have been taken over by the progressive left. The SPLC, on the other hand, might simply be a creature of the progressive left. I don’t know its origin or history.
“The Southern Poverty Law Center was founded by civil rights lawyers Morris Dees and Joseph J. Levin Jr. in August 1971 as a law firm originally focused on issues such as fighting poverty, racial discrimination and the death penalty in the United States. Dees asked civil rights leader Julian Bond to serve as president, a largely honorary position; he resigned in 1979 but remained on the board of directors until his death in 2015.”
see “Notable SPLC civil cases on behalf of clients”
https://en.wikipedia.org/wiki/Southern_Poverty_Law_Center
“Dees was one of the principal architects of a strategy that used civil lawsuits to secure a court judgment for monetary damages against an organization for a wrongful act. The courts could potentially seize organization assets in order to gain payment of the judgment. Dees said that the aim was to gain large judgements which would ‘clean their clock’.”
https://en.wikipedia.org/wiki/Morris_Dees
“Leo Max Frank (April 17, 1884 – August 17, 1915) was an American factory superintendent who was convicted in 1913 of the murder of a 13-year-old employee, Mary Phagan, in Atlanta, Georgia. His trial, conviction, and appeals attracted national attention. His lynching two years later, in response to the commutation of his death sentence....”
“On the afternoon of August 16, the eight cars of the lynch mob left Marietta separately for Milledgeville. They arrived at the prison at around 10:00 p.m., and the electrician cut the telephone wires, members of the group drained the gas from the prison’s automobiles, handcuffed the warden, seized Frank, and drove away. The 175-mile (282 km) trip took about seven hours at a top speed of 18 miles per hour (29 km/h) through small towns on back roads.... A site at Frey’s Gin, two miles (3 km) east of Marietta, had been prepared, complete with a rope and table...The New York Times reported Frank was handcuffed, his legs tied at the ankles, and that he was hanged from a branch of a tree at around 7:00 a.m., facing the direction of the house where Phagan had lived.”
https://en.wikipedia.org/wiki/Leo_Frank