I think the argument is that there are many ways to compliment someone that aren't sexual, and that sexual statements (whether compliments or otherwise) should not be used in work situations: that even in a situation where a sexual statement is taken as a compliment rather than an offense, it is still inappropriate for work.
c) a standard for behavior which may have unintended consequences. If you want to regulate a behavior, you should be able to demonstrate that the harm imposed by the regulation is less than harm prevented by the regulation. In my opinion a blanket ban on sexual comments in the workplace probably does more harm than good.
