They inspire people who follow their precepts to angrily fight
against some perceived establishment. They're all products of
the 19th century and are considered heroes in 21st century
academia.. It's true that when people like one, they usually
like all three. Sort of, "If you like Darwin, you'll LOVE Marx.
If you like Marx, you'll LOVE Nietzche. And if you like
Nietzche, well, have WE got a treat for YOU!"