Does he have a hard time seeing at night? Are the lights on when you approach him?

I ask, because I was sitting in our living room one evening with my Grandma's Miniature Schnauzer watching TV (no lights on) when my older brother (he's almost twenty) walked into the room with his sweatshirt hood up over his head.
Molly growled, jumped off the chair, and ran over to him barking fully intent on taking down this "intruder". When she got closer she realized it was Jake and she jumped on him and rained him with kisses.

I would feel really apprehensive punishing or startling an already worked up dog, as that can just add fuel to the fire. I'd try to find a different behaviorist that works with positive reinforcement and see what she says about the issue.
Did the behaviorist you contacted earlier give you any idea as to why he was growling?