It was brought up because you make the ridiculous assertion that Luffy's kryptonite is blades, and that he is weaker to them than a normal person would be, which simply isn't true.
His rubber bones don't give him inferior defense, that is complete bullshit and you should be ashamed to say such retarded nonsense. Do you not remember HONE FUUSEN? His bones are harder than steel. If the rubber Luffy was made out of was weak in the way you suggest he would snap if he tried to stretch too far regularly, and definitely wouldn't be bulletproof.
Luffy had his haki defense down, and was not even trying to minimise the damage by twisting or rolling with the kicks. He literally would have taken less damage if he had been sleeping and let himself fly away rather than stand his ground but not force back. This was shown clearly, but people who speed read miss this. Probably should re-read the manga rather than spending your time spreading misinformation.
Luffy tanked Kaido's first attack last chapter using a cross arm block when taken surprised and in a subobtimal blocking stance, in base.
Kaido's power>Zoro's. so story closed.