The end-season player awards are based on subjective voting, you know that. It's a system where people vote based on their gut and what they think they saw, rather than statistical truths.
Looking at who's most likely to give up a TD isn't a stupid argument, but it's an incomplete one. That's why I included "TD rate against" in the little formula that I made up. Even before I added the "completion % against" metric, Porter was the worst CB because of the amount of yards he gave up per completion compared to the number of plays on the ball that he made.
Porter gave up more than 13 yards per catch and only made a play on the ball 10% of the time. Compare that to the 2nd worst player in the group, according to my formula, Leodis McKelvin. He gave up 11 YPC but he made a play on the ball 17% of the time. McKelvin and Porter had the same completion percentage against and similar YPC given up, the difference is that McKelvin made plays.
It's difficult to look at some of Porter's stats with any definitiveness because of the number of games he played. While it may seem like you can just take his TD per attempt rate and compare it to guys who played 3 times as many games, you can't. The fact that the sample size for data is smaller means that it is more prone to be skewed. In this case the data gets misrepresented because there are only so many TDs that can occur in one game. As an example, it's more likely for a player two give up 2 TDs in two games than it is in one, even if there are an equal # of targets. This is due to the amount of times that a CB will face certain situations in a given week. That's why Adam's method of looking at the TD/G ratio isn't as inaccurate as you might think.