Sorry, but the only reason that clause in the 14th amendment seems "obscure" is because American schoolchildren have been prevented from learning anything meaningful about the Civil War. @maddow

And because many American adults *refuse* to learn this meaningful fact about the Civil War: the Confederacy and its soldiers committed treason. @maddow

You can tell this "obscurity" comes from active suppression of Civil War history because EVERYONE knows they have 1st Amendment rights or 2nd Amendment rights, but very few people know that the 14th Amendment extends those rights to the state and local level.

"equal protection under law"
"due process"
"natural born citizenship"
everybody knows these phrases from the 14th amendment. the reason they don't know clause 3 is because it memorializes the historic fact that the US had to protect itself from seditious ex-traitors taking over.