As a Brit, but not a teacher, and having checked Answers.com:
reflexive pronoun: Information from Answers.com
The noun has one meaning:
Meaning #1: a personal pronoun compounded with -self to show the agent's action affects itself
In your case, if it read: "He slammed himself against the door", then "himself" would be correct, because he is doing something to himself.
If he slammed the door, he is not doing something to himself.
Hope this helps