It took awhile, maybe a full ten minutes of silence before Stiles realized what was going on here. Yeah, Derek was actually trying to show him how to be a vampire. An alpha werewolf wasn't chewing out his neck, instead he was trying to help.

"Look...I'm sorry. You're trying to be the big bad brother wolf, but.....I'm just not ready to deal with telling my father all this stuff. He risks his life enough every time he goes to work, he doesn't need to know this...."