Is it legal to post degrading signs in the workplace?

Degrading signs in the workplace are never appropriate and can be construed to be discriminatory and create a hostile work environment.  In Michigan, the environment has to be so hostile that it is beyond simple teasing and it must actually change the work environment.  It has to be severe and pervasive.  This is usually based on a reasonable person standard -- in other words, would a reasonable person conclude it is hostile.