ISN Software Software Engineer(Internship) interview questions

The first interviewer I got, started asking me difficult/confusing questions on C# even though I told him I am not so proficient in it. He kept on asking more and more such difficult questions. Idk what he wanted to test me for? A simple question I have. If I don't know C# in dept and if they don't want me, why would they call me to second round? Just to humiliate me? Again, it was a interview for an intern position, if they expect I have knowledge of a senior engineer then am I at the fault? I have given 6-7 interviews in my career and this was the worst experience. Even if i would get an offer and I would accept it, I would still hate what they did to me in the Interview.