There are so many holes in your "evidence" that it shouldn't even be considered evidence. The fact that you think Cousins is responsible for how all three of the guys played offensively is asinine. The only players Cousins really guarded were Lopez and Evans and by no means did he guard them the entire night. Lopez is one of the best centers in the league. In fact, he is leading all centers in scoring this year. It's tough for anyone to shut down that caliber of player especially when his supporting cast is knocking down jumpers left and right which tends to lead to less help defense.
Stats don't show the quality of shots these players took. You could play the best defense in the world, but the shot could still go in. Sometimes no matter how good of defense you play, your matchup will be making them all day. Some nights it just happens that way. As long as he is contesting their shots, I could care less if they go in because more often than not we will reap the benefits. Please don't throw shooting stats at me and suggest that he played poor defensively. A lot of other variables come into play.
In terms of Thornton when he scores 24 points and receives a B grade, it is usually because he did it inefficiently. There is also the case to be made that he doesn't contribute to any other facet of the game (defense, rebounding, passing, etc.). Unlike Cousins who does offer more than just scoring. So as many have mentioned, please take a step back and take the blinders off.