I'd be tempted to ask, very nicely, about the poster. Something like "I've never seen that poster before, what are you hoping people get from reading it?" If they say, "people are all the same," then you have some important information about their likely inability to work with differences that matter. If they say, "that there are differences between people, but not all differences matter (ex. skin color, height), so we treat everyone with respect," you know you are dealing with a more positive intent.
That's just my personality, though.
