One, last I heard, they STILL don't give them anything for the pain beforehand.<quoted text>
And what is known now can be refuted in the future as more is discovered. One example: it used to be known that newborn baby boys don't feel pain, therefore a circumcision was done with no anesthetic. With more study that was proved false. How many baby boys were subjected to the pain of their foreskin being sliced off before we wised up?
Two, it wasn't "known", it was ASSUMED.