"Yeah, yeah, yeah." He chortles, not really caring to 'deny' or 'confirm' if Kokichi is actually his favorite or not. He'll just let him have the satisfaction of declaring that for himself. "Oh, geez: now you spitting philosophical lines or whatever, kid? That kind of thinkin' ain't good at all. Life can still be sweet!" He tells him, though he doesn't completely disagree; if anything, it was the complete reverse for him. Maguro's life at a younger age... was far more sour. Of course, he probably shouldn't say that to Kokichi...
"Yeahhh, you're only one of those things." Which one? He won't say! "Well, you're not wrong, though: a lot of my students in my homeroom class are coffee and tea drinkers. Long as they weren't forced to like it, nothin' wrong with that." Insane and power-controlling parents... he knows a couple of his students know what that's like... including himself.
"Cause of my folks...? Hah! Nooo sirree! If they told me to like sour stuff, then I would've haaated sour things! No, I like it because it's my favorite, regardless of age. I was the kind of kid where if my parents said one thing, I'd do the other!"
In fact, his expression was turning sour, itself, just thinking about his parents. It was safe to say, Maguro's relationship with them was anything but sweet.. Then after a small pause, he realizes he might have said a little too much and instantly, a (semi-forced) smile is right back ion his face, along with a thumbs up!
"...S-So anyway!!! Don't anyone make you tell you what you should like, okay? Not even your folks! Your personal tastes and likes and all that good stuff are things you should discover for yourself, for you! Yeah!! And heh, maybe I'll just sap your 'youth' energy at the same time so I don't grow older! Then we'll both stay at our current ages forever!"
He laughs, though he was serious about the little 'life lesson' he gave Kokichi: to not let anyone force you to like things just because they said so. To him, freedom of expression and being yourself was things he followed to the very T, even back in his delinquent days. It was something he wants his students and his son to always keep in mind, too.