I'm new to this, so maybe someone else can correct me if I'm wrong, but:
Maybe your snake is learning that if he is aggressive or hostile you'll put him back, which seems like what has been going on.
I've been watching Jordan Shaw's videos, and so far they've been helpful for me to understand my snake's body language and thought process.
https://www.youtube.com/watch?v=HnWv7XOd-X8
https://www.youtube.com/watch?v=f-TjNKrsQEQ
Like I said, I'm really new to this (just got my first BP 2 weeks ago!) but hopefully this can shed some insight and help you out a bit!