User blog comment:Schneeze/Eh, Nekomimi/@comment-15108745-20131101023751

Adam is probably a Faunus if White Fang are as extremist as Weiss says. They would probably be outraged at getting the help of a human in accomplishing their goals.

As for why Blake decided to go to Beacon, I would look at  the quote in front of the Black trailer, "Your hopes have become my burden. I will find my own liberation..."

I interpret that as: The hopes of White Fang were too much for her and became a burden instead of something she truly could believe in. Thus, she decides to not associate with them and tries to find her own way to fit in with human society.