Both parents should use carrots and sticks. In general, it's probably a good idea to start with carrots and then go to sticks (though admittedly I often rush to the stick).
Note: when I say stick I just mean limiting his TV time. Of course,
most punishment at this age is not going to be much good.
I would counsel you to not say or believe that-- it will be a self-fulfilling prophecy. I would argue a) the discipline and self-control you model and require of your kids at a young age lay the foundation for later, even if they don't "Get it" now, and b) it can be effective. Effectiveness will look different for different kids. And appropriate carrots and sticks will be different too. Limiting TV time may not be enough-- it is effective in that excessive tv time may make behavior worse in the first place-- kids need to hear and understand the what's and why's of right and wrong (in my opinion at least).
The kid we have the most problems with is our 4.5 y/o. There are hours, days, and weeks where he's very difficult. But we can also see positives, particularly in how well-behaved he is when he's out in public or when he's at someone else's house, and with certain traits we are seeing at home as well.