I think Sattya never respected Antara. His mother always chose Raghu over him- That anguish is making him snatch everything and everyone Raghu loves. To him, in this way he can hurt both Raghu and his mother. Sattya is a kind of man who will do exactly the opposite what he will be told to do. He knows that his mother dislikes Antara. He will convey again and again in front of DM that he wants her. His mother told him to use Antara and then throw her. Sattya will try to show that his love for Antara is eternal, beyond the physical attraction etc etc. He will never admit even to himself that all he is doing is just to show Raghu that he is bigger than him.
About that dupatta throwing after effect, Sattya was smiling to himself. Because he saw in his own eyes that his mother was absolutely correct. Antara doesn't give a hoot to him and their relationship. She is already Raghu's and whatever Sattya does, it is not gonna change.