I think a lot of people are missing the point Yahtzee was trying to make: that if a game can't be bothered to make a good single player experience, then it shouldn't have bothered to put one in at all. The point of having the two modes at all is to give players who like or dislike playing with others the available option. The two camps can be happy without watering down one half to appeal to the other. A good game would have good single and multiplayer modes that cater to both and don't screw with each other.
Not only did EA put in a single player mode without making it actually good, but they had the gall to try passing it off as on par with the multiplayer. If they didn't want to bother with Single player, they should have just made it just multiplayer.
And yes, he's writing off an entire game mode just because the one he's willing to play sucks. But then again, so long as the multiplayer mode functions, it's not really the game itself that's making the multiplayer good. It's the players making their own fun with each other. Complaining that he didn't give the game a fair shake by ignoring multiplayer ignores the fact that reviewing the multiplayer portion in any capacity other than "does this function?" wouldn't be reviewing the game itself. It'd be reviewing the players. And that's not what he's here for.
He reviews the single player because that's part of the game and the fun hinges on how good the game is, not how good the players are. And in that respect, the single player mode (and by extension the game itself) is very poor indeed. If the multiplayer is all that counts, why bother making new multiplayer games at all? This is why Team Fortress 2 is still profitable years later; people enjoy playing with each other, and TF2 is an established place to do that.