Sunder paused for several long moments, mildly aggravated and annoyed at the girl's tone and attitude. She was interesting, and there was a certain relief to her frankness, but he also didn't become a sorcerer to be mocked and degraded. He slowly turned and looked at her, a warning, threatening light in his eyes. 

"A Necromancer planned to use you in his schemes, somehow. Simply taking you from him might have foiled a plot that could have brought the rest of the Allied Lands to its knees. More than that, sending you to Whitehall would teach you how to become integrated into society- meaning that you would be able to help fight against the Necromancers, in time, and you also won't be here, where I have to keep a constant eye on you. 

"I am a Lone Power because I did not see enough getting down in the normal society of magicians. I am a Lone Power because I made it my goal to ensure that the loss of life to anything that I can stop remains at an all-time low. So, if you must know, you could probably attribute my goals to keeping a clear conscious. Does that satisfy you?"

Sunder turned back to his breakfast. If she insists on mocking him, he'll just freeze her, via compulsion spell. Given what he's observed, being absolutely unable to move without any way to get out of it would probably be enough to stop.