The only priciple that really applies is showing humility and meekly following the direction of the elders and the higher ups in the societies power structure. You cannot outright refuse an order from an elder or higher without a sound scriptural reason agianst it. There is no burden whatsoever for them to show a sound reason for it. The simple justification that someone could be "stumbled" is more than enough. Failing to humbly follow their direction is grounds to punish. That punishment may be the removal of privledges and could, if the person showed a rebellious nature, include disfellowshipment.
This type of petty control and lack of balance is one of the fundamental issues I have with being a witness. To most who are active, this is dismissed as being a little thing and should not be harped upon or used to cast doubt on the "Truth" in general. They simpley have been too well trained from using sound judgement and will tend to follow without question (openly anyway) any rule, or suggestion without a regard to it being scriptural, ethical, or moral. After all it is not for "man to judge his own footsteps".
To me, however, all people have both the right and responsibility to judge the correctness of thier actions. While a person may choose to do something to "fit in" and this facial hair rule might apply, there are too many of these petty restrictions and controls without sound scriptural basis for me to simply ignore. These rules by themselves would not be such a deal breaker for me if it were simply social deterents (frowns, disaproval, ect.), irratating and judgemental, yes, but unethical, no. To enforce these petty behaviours with the possibility of the most extreme punishment that witnesses have, disfellowshipment and death at the big A, makes this both unethical and tyrannical. Granted, usually all that happens is removal of some 'privledges' but ANY outwardly noticable rebellious attitude could result in a Judical Commitee at some point.
In fact if I were to speculate, I would think that this type of seemingly little and petty rule helps weed out those who have an independent spirit thru the simple aggrivation of how utterly rediculous it is.
Sorry for the spelling/grammatical errors to the grammer nazis. In a rush and didn't want to cut and paste from MS Word.