it takes more than a tie to be a professional pilot, having said that, appearance is obviously very important to the customer and your employer. if the company wants you to wear a tie then so be it. are phantom or superman ties ok??? (just kidding)
neat and tidy casual clothes do not detract from the image of a company.
our instructors wear company supplied work shirts and trousers. the shirts and jumpers have logos on the pockets, with no tie, and we haven't had any complaints in fifteen years.
i do think it is pretentious of some pilots when you to go into the local town and see instuctors in reflective taped flying suits with badges that say instructor and wings and other paraphernalia hanging off them. some companies in australia have their new instructors wear epaulets. a bit over the top as well.
you don't see many grotty instructors around, all of the blokes i know in instructing are proud of their jobs and if you are the same then it follows that you shoud be proud of your appearance.