What exactly is "slut shaming", and why is it so wrong??

" I probably made them cautious with my condom lectures and don’t believe if a girl tells you she’s on the pill"

My condom lectures were geared to both my son and my daughter with the message that they were the safest thing to use to prevent STDs. No love without the glove. These talks weren’t premised by a “girls might lie” thought process.