I don't think it's bad reasoning at all. There is a BIG portion of people who play tdm because of the reason he said. And as far as arms race goes it was a limited time game mode so you can't really say how popular it would be if it stayed. Personally my opinion of AR is pretty simple. Like everything else in this game they wanted to make it even easier for noobs to get streaks .
Back on topic. Because they got rid of barebones tdm is the next best thing for those who want to see how they play against the other team . Believe it or not there are many people who find it more enjoyable to actually kill people with their gun skills instead of sitting in a corner while the game AI does it for you.