I disagree.
The problem is often strict letter of the law types who dont know when to use discretion in spirit of the law.
In real life most rules do get bent a little and the key is knowing how far and when to do so.
I dont think that starts a slippery slope, the original standard stays about the same and if anyone goes too far then they are pulled back - so same starting standard does not change
My work example was an example - sure, you can argue what if next person did this or that - but reality is nobody else has over done the rule bending either and the original standard has not changed.
Like many work places there are a range of options for work tops, all in same colour/logo but different styles - so you pick your preferred ones.
Occasionally somebody might wear a non work top - if they were only coming in for a few hours or something, and that is ok too.
It doesnt start an avalanche of everyone wearing non work tops all the time - because we are adults and understand degree and context.
Likewise poster who was refused entry wearing high heeled blingy "flip flops" - had she been allowed entry, as common sense would say she was wearing suitable footwear in spirit of law, that wouldnt start an avalanche of people trying to get in with rubber beach flip flops or change the original standard.