"Considering your track record, consider it a very well educated guess," Stiles tells him, his brows drawn together angry. He really is angry, though not really at Derek - but convenient target is convenient, so there you go, sorry buddy.

"So you're not behind - a pack of Alphas." Stiles is immediately derailed from being glad that Derek's about up to speed with them, to being abjectly horrified. "When was that? How long have you known about that? This is what I mean about not sharing shit, asshole!"

He is basically yelling, waving his arms around at Derek. Some of the aliens are starting to look at them funny, so he tries to calm down a little, but he's still seething.