If I had a dollar for every time one of my poorly dressed students attempted to argue that appearance had no factor in presentation I would fly First Class on every trip I take. It really does not matter what you think is fair or right. Even as casual as our society has become, we still evaluate people based on their clothing and grooming. We all do this, and no amount of complaining will change this.

If you want to be treated as a Ph.D then wear the appropriate costume. Currently you are dressing like beach bum and probably being treated like one as well. This has nothing to do with "dress codes" and everything to do with social expectations.