What makes it arbitrary and indefensible. The affected not LIKING the policy, the affected not making themselves aware of the policy does not negate its validity.
What does UA get…maybe just a few passengers each flight that don’t look like they just rolled out of the steam room of their gym. Maybe just a few less uncovered legs (an butts - given the length of some ‘normal’ short).
Maybe the folks in first and business appreciate flying with other well dressed folks and will continue to support the company which affords them this opportunity.
Not everything is a civil rights/gender/oppression/SJW issue. Sometimes it’s just a ‘rule’…which seems to have become a nasty four letter word.
@busdriver11 I think you are abused, oppressed, discriminated against and you need to act NOW…what a horrible thing to have to adhere to a dress code in a jump seat. 
Along these lines. I think surgeons should be able to show up in their golf attire. Nurses should be able to wear tights and tunics. Heck, your waiter should be able to come in off the beach in swim trunks and SPF 50 and go ahead and serve you - we live in a beach town.