Worthy of Respect

Interesting phrase choice.
So the man is a noble within the Known World of Mystara (essentially the Gazetteers). It is far more certain that when a PC noble meets other nobles from far away nations (Red Steel, the unchartered continents Davania and Skothar and even the lands in Brun not covered within the Gazetteers as well as the Hollow World) or even those from another setting altogether) they won't recognise each other.
You seem to think a DM ruling this way is an affront to the player or at least his creative choice.
Meanwhile the common place view would be to appreciate the setting and the table's fiction.