After the dissolution of the union with Montenegro Serbia inherited the old Yugoslav constitution and so it was a one country federation. So it needed a new constitution that abolished that superfluous layer of goverment. This offered also the opportunity to update the constitution a bit. But as fits constitutions this update was not meant to be controversial - as was shown by its 96% approval rate.
One might qualify the statement that Kosovo is an essential part of Serbia as controversial. But the writers of the constitution had little choice here. Any softness here would have been interpreted as that Serbia has given up on Kosovo and that would have weakened its negotiation position in Vienna.
Yet the International Crisis Group (ICG) and the NGOs that it funds still found it necessary to attack the constitution from all fronts. I have not the impression that this criticism was meant to achieve improvements. Instead the goal of the attacks seems to demonize Serbia. They show much resemblance with an old election tactic: if you throw enough dirt at someone some of it will stick. If you want to read the dirt the ICG is throwing please read here on James Lyon's blog. Allthough some of his minor criticism is valid, the great majority of it consist of putting things out of context.
After the referendum (end october) the ICG continued its offensive with a report "Serbia’s New Constitution: Democracy Going Backwards". As this is a bit late to correct things this can only be classified as destructive criticism: sowing dissent and arousing hatred.
It is not clear what the aim is of this propaganda. Maybe some people at the ICG fear for their jobs now that the organisation is becoming superfluous in Europe?
But I do believe that mr. Soros should do some serious thinking about what he is doing with his money. His stated aim is to promote democracy in the former communist countries, but the organisations that he supports - like the ICG - seem bent on creating havoc instead nowadays.