I think that we have to be careful when applying this class to real life debate. It is, after all, a philosophy class... and while the ultimate goal is to help us understand the way arguments work, we are often talking in very different terms than we would in actual discourse.
When Walter says we should try to make our opponent's argument look good, he's saying that when we consider their argument, we need to disregard our potentially conflicting opinion. We should break it down and reconstruct it so that we can see how strong their points might be. If you take every point an opponent is making, and do your best to reconstruct it in the most logical and sensible way that they could possibly have put it, then you're more likely to understand their argument, even if you don't agree with it. You are supposed to set aside your own opinions, and strengthen the argument you're looking at. Once you understand your opponent's angle, you will know what you need to say to counter it.
If you understand every facet of your opponent's argument, and they haven't prepared as well as you have, you're in a good position to win any debate against them. Knowing the strengths of the opponent's argument is far more important than knowing the weaknesses... because if you know all of their strongest arguments and are prepared with legitimate counterarguments, then you will come out looking stronger. On the other hand, if you attack their weak points without dealing with their strong points, you might end up looking like a bit of an inept jerk for only fighting the easy battles...
Unfortunately, when it comes to presidential/political debates, it is rare to find someone who is more concerned with honesty and legitimately strong arguments than they are with votes and/or pleasing their lobbys. I won't get into my personal politics, but I will just say that we are taking a philosophy class on logic.... and in my experience, politics isn't particularly logical.
Cheers,
Tracy