You know what I would tell a doc who said something like that?

"Well, if you people would really pay attention to the symptoms I had, I would have been diagnosed much younger...so it's your fault!"

There are no age restrictions in any information I've read...in fact, I have read information that states that the older you are when diagnosed, the more likely your MS will progress more quickly.
IMO, that's because the docs were denying us older folks a diagnosis instead of getting us on DMDs asap...