Welcome to the forum...I beleive its an individual dog situation...many different equations can imerge of questions...but, your vet should have weighed out the good and the bad, and should have your dog's interest at hand...but, vet's are human too...
Peekawho notes were right...the vet here...on forum...post this comment to them...I am very impressed with the response time and answers are very well commented by Dr. Cheng...
Much luck to you and yours...give the fella a hug from me:o)
This is a great question for Dr. Cheng, who answers questions for free over on the Ask A Vet forum (link on the right side of the page under Related Expert Forums)
I'm sure people will weigh in with their opinions, though. Has your dog been having prostate problems or UTI's? There are very good reasons to neuter even an older dog.
Is he in general good health? Has he had the blood work that is usually recommended for senior dogs?