The full transcript is:
(They go through to the inner room, and we see Data's reflection in a full length mirror. He is sporting a full set, a beard like Riker's)
LAFORGE: Did you damage your face, Data?
DATA: It is a beard, Geordi. A fine, full, dignified beard. One which commands respect and projects thoughtfulness and dignity. Well? Opinions?
TROI: It's er, very different.
DATA: When I stroke the beard thusly, do I not appear more intellectual?
TROI: I'm sorry, I have to go now. Goodbye.
(Troi leaves, quickly, laughing)
DATA: Why was she laughing?
It is clearly not the case that Geordi doesn't recognize a beard when he sees one. Obviously the entire scene is played somewhat for comic effect. The comment by Geordi can be understood as some combination of:
- Rhetorical remark for comedic effect
- Geordi probably didn't think Data was capable of growing a beard
- Geordi may be guessing that the beard is simply applied to his face (not grown), which is likely. (But how exactly does Data's hair work to begin with?)
- Geordi guesses that he may have applied it to cover up damage to his skin. (One assumes that it's easier to glue on a beard than to fix his integument.)
- Geordi doesn't know what Data's motivation is (which Data then explains)
Bottom line: You're stretching too far. It's not that complicated and doesn't required an exotic explanation about why Geordi doesn't recognize beards. To quote @Martha: It shouldn't be interpreted as "what is this stuff on your face?", it should be interpreted as "why is there hair on your face?"