The General Officer that testifies on various subjects is there to be questioned. Even when the questioning becomes hostile the duty of that officer remains the same. To answer the questions in a professional and honest manner. As to how you address a Senator; while sir or ma'am are acceptable so is Senator and it is really up to the senior in the situation as to the form of address he or she prefers. However the distinguished Senator from California should review Army policy as well as USG policy on protocol with her people.

Take a look at the coverage of the Senator's remarks. She came out looking like an arrogant snob with a sense of entitlement. The General came out looking like a quiet professional. Had he lashed out at her he would have probably been charged with contempt of congress, relieved for cause and who knows what else.