I agree with most of what most people have said in this thread. You definitely did the right thing to refuse to give this guy the boa. And window & door locks, as well as a lock on the boa's cage are a good idea, just in case.

I will not go so far as to say that this guy is/was not a true friend. People have bad days. Most people blow up at least on occasion. If this guy has shown other signs of being a true friend, and he comes back and apologizes for his poor behavior, then maybe he really is a good friend.

I still wouldn't give him the boa. The issues with him being a snake owner are much more than just one blow up.