[Mithalwen]

We know that Boromir, unlike his father and brother was not so interested in lore and was in some ways alike to the men of Rohan who have a great suspicion of Lorien. Even Faramir who is more learned and perhaps open to other cultures is wary of Lorien. Maybe Rivendell having been forgotten by most was less threatening than the closer realm that was the subject of rumour and superstition.

This prejudice is reinforced by Galadriel perceiving his developing desire for the Ring.

Boromir certainly doesn't embrace his alleged distant elven ancestry..