Jim, I suspect the word is actually far older than you surmise. While
enjoying my nightly pipe of opium, mixing my Forum reading with my nightly
dose of Lewis Caroll, I encountered the following use of the word
"bitchslap."

"'I don't know what you mean by "bitchslap,'" Alice said. Humpty Dumpty
smiled contemptuously. 'Of course you don't- till I tell you. I meant
"there's a nice knock-down argument for you!'" 'But 'bitchslap' doesn't mean
"a nice knock-down argument,'" Alice objected. 'When I use a word,' Humpty
Dumpty said, in rather a scornful tone, 'it means just what I choose it to
mean- neither more nor less.' 'The question is,' said Alice, 'whether you
can make words mean so many different things.' 'The question is,' said
Humpty Dumpty, 'which is to be master- that's all.' (Lewis Carroll, Through
the Looking-Glass, Chapter 6.)

    Oh, my.  Things get curiouser and curiouser.  Now I'm a misogynist.  I
think I'll take a little sip of this bottle that says "Drink Me."

    Terrell