The title is a little frustrating for me because this feels like one of those things that you should not have to explain to adults in the 21st century. And yet, here we are. From the linked piece:
So, while I understand that Hillary Clinton isn’t everyone’s cup of tea, I can promise you this much – she’s a hell of a lot better than any Republican alternative. So to all of you liberals who loathe her and feel that voting for her would be “selling out,” do you really want a Republican president potentially replacing four Supreme Court Justices?
It will be an argument that neoliberal Democrats use early and often: vote for Hillary, otherwise the brownshirts will be choosing our next Supreme Court. They will use it because it is fairly persuasive; Democratic nominees to the Supreme Court are typically more liberal than Republican nominees to the Supreme Court, and it seems as if every Supreme Court ruling is being decided with a knife’s edge.