First of all, please excuse me for my grammatical errors, English is not my native language.
I disagree with the decision to DQ the badminton players, why? because in my opinion, those 8 players are already gone through to the next stage, logically, they already "win THE match" using their best efforts, and did not need to do anymore effort to win another (there's no point in winning another, they already gone through right?). Imagine this, in archery, or any other sport, when you already won 1st, 2nd, and 3rd set, the match is stopped, because we already got the clear winner. then why we need to force them to play the 4th and 5th set?
Now back to the badminton, of course that final match is to determine the group champion, but in the players' vision, what is more important? waste so much energy to win and be the group champion or to save energy, and go all out for the next bigger matches? I don't wanna be a hypocrite here, if I were the chinese, I would do the same, just play as fast as possible, not care for winning, and go back for nice rest for my body muscles to prepare for bigger match tomorrow.
I don't think this is cheating or disgrace, this is pure strategy. And trying to lose so that I don't have to defeat my own compatriot early is also a strategy (national strategy I must say?), and nothing wrong with that IMHO. I don't have problem with that at all. In fact, they were not really trying to lose, they have already won and gone through remember? they're just using the extra match to gain advantage by choosing the opponent, IMO it's smart, not cheating.
Now about the angry spectators, in my opinion it's their own fault in the first place for watching that match.. what do you expect from two teams that already gone through? nothing! of course.. that match didn't matter.
Actually, all of this is very normal to me, and I kinda surprised the officials took this very seriously.