Thank you for sharing your feelings on this one, I hadn't heard of "graybeard" categorized that way by anyone before, though I can see your point-of-view and respect it.
That being said, if the person was an actual human being, and subsequently had a graybeard (as I do!) - would that still be offensive?
I don't intend to be combative, simply trying to learn!
If you really feel that they color and presence of their facial hair was the best way to describe whatever it was that felt relevant to mentioning them, I can't really call that offensive.
But the term "graybeard" is known in these circles as a reference to an older, always male, programmer.
What actually matters is that they've been around the block enough times to understand (for example) that Rust probably will not solve every programming issue known to current programmers. Their gender and facial hair status is not really relevant. "Corner office grump" would be another term that I'd find entirely acceptable: non-gendered, unconcerned with physical appearance, but encapsulating much the same sort of personality that "graybeard" is attempting to evoke.
That being said, if the person was an actual human being, and subsequently had a graybeard (as I do!) - would that still be offensive?
I don't intend to be combative, simply trying to learn!