There is no such thing as cage aggression, or aggression in general when it comes to snakes. The animal is either being defensive or has an aggressive feeding response. Was he just fed? If so he could have still just been in "feeding mode." My milk snake does the same thing after feeding. Pet stores don't use hides sometimes because the animal is more likely to sell if people can see it. I think it is a bit cruel. You may have a hard time getting him to eat for you if you take him home since he is probably already stressed.