@The:
Oh please Luffy hasn't done anything a person like Kaido would deem as worthy of his attention/respect. What has Luffy done exactly? Beaten a couple of shichis and that's it. Shichis that are fodder to Kaido. So why would he even act like Luffy is anything different? Has Luffy taken down another Yonlou? Has he taken down anyone even close to Kaidos level? No he hasn't. Kaido has every right to look down on ANYONE except like 6-7 people in the entire world.
And all the ennies lobby, marineford and impel down crap is only important to us readers who know the whole story. To Kaido, why the hell does it matter if he did all this crap if he didn't even beat anyone above fodder level? Why would Kaido acknowledge all these things that he considers nothing more than games?
Kaido is for all intents and purposes a god. Everything Luffy has done until now is nothing, that's who Kaido is.
Everyone seems to miss the fact that Kaido not taking Luffy seriously is a good thing since if had picked to go after the straw hat alliance now that they have split up into groups he would wipe them out since they need a team effect to take Kaido down he will be the first yonkou to go which means he will need a team effect i can see Kidd joining their alliance he will tell the straw hat alliance of Kaido's devil fruit and teamed up with luffy and law at the auction house which would be Oda's way of foreshadowing their team up also big mom will be the first yonkou that luffy takes down by himself since his rubber fruit gives him a advantage over big mom's acid fruit so it will be like the enel fight where luffy had a fruit type advantage then luffy will fight blackbeard later on who has a fruit type advantage over luffy i can see luffy having a duel with shanks before blackbeard kills shanks where luffy will lose to shanks and beating blackbeard will show that luffy is better than shanks.
To be fair it seems that he is sending Kidd to scare Luffy away by telling Luffy how he got beat by Kaido which means he knows that Luffy and his pirate alliance can do some damage if they attack.