Oden literally said he wanted cut kaidos head off multiple times.
Zoro has killed humans mr 7 magistrate etc
Magazine hints at the legend of a new ryuma being born slaying an eastern dragon.
Yonko are not luffys dream. Being pirate king is luffya dream.
Actions speak louder than words and the colloquial of wanting someones neck or head doesn't mean literal killing in all cases. Oden had his chance due to Kaido's sloppiness and didn't want to capitalize on it, instead showing mercy.
Having to resort to an offpanel backstory before he became a Mugiwara doesn't help your case as much as you think it does when he has been in the present for almost 1000 chapters not killing humans.
Magazine bs hype.
Luffy has explicitly said as part of becoming the pirate king he needs to take down the yonko, it's part of his dream. It's like saying if Zoro ends up being a stronger swordsman than Mihawk (or a hypothetical murderer of Mihawk) he doesn't need to prove it to fulfill his dream, having sufficiently high base stats and skill will automatically transfer the title over to him.
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He has said he will take her down after Kaido, to do so before taking down Kaido would be a tactical mistake considering they are in Kaido's territory.
He beats up Kaido, his crew loses morale and the chances of winning the war increase dramatically.