John McWhorter on the history of taboo words:
In our society, the main taboo is no longer sex, but race. Such things evolve: the big taboo for medievals was religion, and thus evasions like “Egads” for “Ye Gods.” Then came sex; that time is all but gone. Now even the edgiest satire tiptoes around using the N-word and if a comedian like Michael Richards slips up on it, he is burned in effigy for weeks.
We consider racial slurs an offense against human beings for concrete reasons but would be harder pressed to express why Joe Biden’s use of an expletive makes him a bad human being.