I'm biased against it, but that could just be because I'm biased against 'fiscally conservative but socially liberal' people.
Well, "fiscally liberal but socially conservative" people rarely describe themselves as such. They have the taste to use more intelligent labels like "populist", "Chistian-Democrat" or "communitarian".
Do "fiscally conservative but socially liberal" people have a strong aversion to "Libertarian"?
Well, "Libertarian" in the US context carries a connotation of extremism and whackery that doesn't fit many FCBSL people. See on this very forum people like King, Oakvale, JerryAR or Clarko.
Indeed the closes equivalent would be "Classical Liberal" and even that isn't a great descriptor.