[Yep, that's par on the course, Stiles is used to Sebastian being equally rude as he is suspicious, or maybe he's just used to people having trouble following his rapid-fire speech and the patented Stilinski logic.
And that's a lovely idea, but unfortunately for Sebastian...]
Wrong. It's not just at this point in time, dude, unless I go back for like a year and you'll stay here all that time, I will always have a) more experience with this place and b) magic.