Allegedly, and this comes from no sources other than campus
rumors, many
fraternities and
sororities began as a sort of social
club for the sons or daughters of
Klansmen.
There are several more, but I can't recall them at the moment.
Also highly allegedly, Kappa Delta on my campus (University
of Illinois at Urbana-Champaign) wore completely white robes extremely
similar to the Klan robes until several years ago. They had rushed
an African-American pledge and decided it would be a very good time
to change the robes.