>One of the things that changed with the American form of the English language within the last 35 years is the use of the word “their”. It is thought and taught to be improper to use such a term. Therefore we must use his/her. What if I had said “he or him”? I just wanted to spread the wealth and not be sexist! :)

FWIW, it's always been improper to use "their" for the singular. All the resources I depend on also object to "his/her," preferring "his or her."

"Their" is fine when the subject is plural.

Tamar