They are enabled to stay relevant because the TV news networks are constantly calling one of their haters in to denounce this or that "racist" person, org, program, etc. NEVER, NEVER, NEVER are their pronouncements challenged by the reporter or some opposing spokesman.
The SPLC has been a hate-filled racist organization for as long as I can remember. Their "credibility" is assigned to them by leftists in the media. Their pronouncements are treated as indisputable gospel with the presumption that if you fail to agree with them...then...YOU"RE A RAAAaaacccciiissssttttt.
They figured out a long time ago that you can destroy people by merely dragging them into court and breaking their back financially.
I have a slightly different definition of "racism" than these agenda biased media zealots...
If you make a decision with prejudice about someone based on their race, you are - by definition - action on racism, and by further definition a "racist".
That operates in all directions, and on all cultures of humanity.
Notice that I don't include religion in that definition. Religion is based upon an individual's choices, not their birth. When an individual uses their belief system as motivation to attack others that is simply wrong, as is any moral system or code that preaches domination of others. Like Islam.
Like the NAACP, the SPLC is now a corrupt organization trying to hang on for relevance. They should be prosecuted under the RICO (Racketeering in Corrupt Organizations) statutes. But there isn't a Federal DA in the country with the courage to do this.