Kidd looks to be on the road to become the tsundere version of Law for Luffy and I'm not really liking that one bit. Oda shold've let him fight Kaido like he intended in the first place instead for going after Big Mom. What a horrible decision made by Oda for Kidd.
Hes not cheerleading luffy, he's fighting the only other antagonist on the level of Kaido. I don't see why he can't smile when Luffy says he'll win.