The cover story is about “[t]he personal papers of John Tanton, architect of the modern anti-immigration movement, [which] contain explosive proof of his many ties to white nationalism.”
This John Tanton, an important, active and prominent anti-immigration leader, has a long and documented history of collaboration with white-nationalists, neo-nazis, powerful antisemites and eugenicists. He has also shown concern about sub-replacement fertility among whites. See my series on Demographic Winter to learn more about this topic.
I have encountered some hard-line anti-immigrant people online, and they repeatedly claim that race has nothing to do with their views on immigration. They then go on to worry about what will happen when whites are no longer the majority in the US. I feel like the SPLC article above will set the record straight.