The phrase in question revolves around a rather odious quote, so I beseech all reading to please suppress your political leanings and focus instead on the meanings of the phrases employed.
In around 1977, Anita Bryant, singer and vocal celebrity advocate of the "Save our Children" campaign aimed at curtailing the freedoms of American LGBT citizens, stated:
"If gays are granted rights, next we'll have to give rights to prostitutes and to people who sleep with St. Bernards and to nail biters."
My fascination focuses on the last part of her sentence - what on earth constitutes a "nail-biter"? Surely Anita Bryant didn't hate onychophagists quite that much?