Silas' previous actions and words were intentional. It was an attempt of his to gain an advantage in the situation he is in currently.
He knew that he would be in a weaker position as he was the one that came to them. Even though he acted all tough on Natasha, the lady in front it him is different.
Also, he knew that he would in an interrogative position as the lady would be suspicious of him and would try to get any possible information out of him.
It would be strange if she doesn't suspect someone who was able to resist the attempt of Natasha who tried to get into his head. Also, even though Natasha is weak minded as she said, the fact that he forced her to the point that she had to bring him to their base before she can get rid of him is something for her to be curious about.
