GameTrailers's Bonus Round is all about GTAIV. Here's Part 1 - http://www.gametrailers.com/bonusround.php?ep=20&pt=1
It sounds like maybe drunk driving has touched his own life in some way and he takes offense to the very idea of it. I wonder if he will change his mind once he plays it, and finds how difficult it is to walk/steer. Those who play tested that scene go so far as to say it is even cautionary about drunk driving.