You can't call it a disgrace. That's very rude. I feel you and other people who are having a go at them in twitter, is being very harsh. When a batsman knicks a ball and is being caught but was not given not-out and he doesn't walk out, will you call him a disgrace? Even that's not in the spirit of game. No! People tell it's umpire's duty to tell him he is out/not-out. Never I have heard the word disgrace in that occasion, but why here ?
Yes, they didn't have a 'spirit of game'. But, they didn't do anything wrong. I again bring this point ( which I highlighted your points in bold), they just went by the rules. They didn't cheat. You cannot call a team 'disgrace' unless they have cheated. (match-fixing, drugs, etc). I never agree with that particular word.
Also, you seem to have neglected the points I made in the end.
Infact if there is anyone who is breaking the rules or not playing with the spirit of game, it's the non-striker batsman who is trying to take a run by leaving the crease early and gaining an unfair advantage.
Look,
If mankading was not there, let the non striker leave the crease and run while the bowler is still taking a run-up. Do you agree with this? No, right? As it's unfair. Now, why do you think it is fair, if the non-striker leaves the crease before ball is being delivered ? Every second, every milli-second matters. There has been many instances where batsman has survived a run-out by being inside the crease by just less than a second. This case is no different than that.
Even here, it could have been a possibility that, batsman went for a run and he would have gotten out if he had reached the crease just one second late. Now that one second (milli second, whatever) late was achieved by leaving the crease early which is not fair.
To sum-up what that paragraph has been, the batsman was gaining an unfair advantage knowingly. Sure, don't call that as 'unfair' and 'out of rules' (yes, again I am mentioning rules) part as an disgrace and call 'in the rules' an disgrace. Disgrace is a very strong word. I don't agree with that and I never will.