The end all, be all answer to this is simple: If God dislikes facial hair so much, he wouldn't have put that in our genes to be able to grow facial hair.
End of story. Anything above this is going beyond what is written. (or NOT written so to speak).
For the record, what I heard officially was that this practice of disallowing beards came about right after Judge Rutherford took over. A lot of the Bible Students (some called Russellites) left after The Judge took control and continued to be Bible Students. A lot of them had beards like C.T. Russell, so of course The Judge didn't want his WatchTower drones to be any thing like the Bible Students, so decreed that beards were forbidden to everyone associating them to C.T. Russell.
So basically, something that started out as Judge JR Rutherford doing to spite the Bible Students, has trickled down to become the "Law of the WT Land", and the younger generation doesn't have a true clue as to why. Even the explanation of it being banned because of the "Hippie Generation" of the 1960's being rebellious is flawed and incorrect, as it doesn't go back far enough. JR Rutherford couldn't stand anyone paying homage to or looking like they are in agreement with C.T. Russell, so hence he banned beards.
Pretty f*cked up, huh?
- Wing Commander