On Arguing with a Toddler

We had kind of a rough weekend. Kate's still getting over being sick and I'm a little tired/stressed from working ahead in my classes and trying to get the house ready for **** ****, aka ******, aka Peanut. (Yes, she already has another nickname.)
And then there is Jack. He's usually a little tired on the weekends from getting up so early to go to school during the week, but he "sleeps in" on Saturdays and Sundays. By sleeping in I mean 6:30ish or later. The last few weeks, though, he has been getting up between 5:30 and six, and it seems to have really caught up with him. I guess this is the round-a-bout way of saying he has been a terror and we have not had the most patience.

Even so, he still manages to make us laugh. (And outsmart us.) Of course, our own tiredness is probably why we even attempted to argue with him...

He has a (Leapfrog?) school bus with the alphabet on it. One of its functions is to make a phonetic sound for all of the letters in song form to the tune of "Farmer in the Dell." Actually, the words don't fit that well. (M says mmmm, M says mmmm, every letter makes a sound, M says mmmm)
While I was making dinner tonight, Jack started singing "R says uuuuh, R says uuuuh" Kate tried to be helpful and told him that "R says errrr."
"No Mommy, R says uuuuh."
"No, I'm pretty sure R says errrr."
This back and forth went on for a couple of minutes, so I thought I would chime in. "Jack, I think Mommy is right. R says errrr."
"No Daddy, r says uuuuh!"
"Well, Mommy and I say errrrr, so that's 2 to 1. So R says errrr"
"You 2, but I a big 1, so R says uuuuh."
How do you argue with that logic? He is the most important person in our house right now, and he knows it.