A positive interpretation makes the sign witty, but I think if you try to look at it completely neutral... it encourages sexual harrassment. Mostly because of the use of the semicolon, which makes the second statement trump the first. If it had said "Sexual harassment will not be tolerated. It will be graded", that would have made both sentences equal, and it would have been clear that sexual harassment will not be tolerated. Now it's not. Now it reads "we don't just tolerate sexual harassment, we grade it".