Sexist jokes, challenging instances of prejudice, and coming back from the dead...

It's hard to explain why instances of prejudice have to be challenged. I once got into an argument with someone I met playing cricket about same-sex couples adopting children, the punchline of which was him honestly and earnestly stating that a child needs its mother as though that was the end of the discussion and he had proved beyond any doubt that same-sex couples adopting was inherently less good that mixed-sex couples adopting. I was shown an article today, which (somewhat terrifyingly) the person who showed it to me seemed to believe to be from a reputable news source, the gist of which is a joke that might have been getting old in the 1960s and would certainly have been recognised as basically sexist and unimaginative by the time I was alive. 
From the perspective of a privileged (privately- and university-educated, white, middle-class, professional(ish), male) person, there's always going to be a challenge to get it. That challenge is very much possible to meet, though, even if it will never be the case that I can feel exactly what it is like to be a woman, black, or whichever minority is in question. There was an interesting discussion on Today this morning about Jeremy Corbyn's attitude to Jewish people and whether he is anti-Semitic, which centred around the fact that because he doesn't consider himself to carry prejudice, he can be guilty of a sort of unrecognised and unacknowledged set of prejudices that are only really apparent to the people to whom they apply, rather than the person who carries them. This is a difficult area, fraught because if the only thing that it takes for a statement to be prejudicial is that someone who hears (of) it considers it to be so, the bar is set so absurdly low that you'd best keep your mouth shut and say nothing at all. The opposite attitude, which I suppose is what libertarianism is all about and what the American constitution tries to enshrine, is to let people say what they damn well please because that's central to freedom. And there is a valuable point to be made in there, because it wouldn't take long to find instances of states silencing dissenting voices, journalists, commentators or opposition politicians where the denial of that freedom is incredibly pernicious. 
So what might we constructively do when confronted by these instances of prejudice? It was a good fifteen-or-so years ago that I first encountered the idea while working with recovering drug users not just of consistently and honestly examining my own prejudices and trying to get rid of them, but to watch carefully for instances of prejudice in others and challenge them when they arise. What might usefully be said to the teller of a sexist joke? In some cases, it might require nothing more than a groan, a gentle reminder that sexism-as-humour is actually damaging, whether to people's self-esteem, or their world view and how they interact with others. In some cases, it might require a more demonstrative response, but in whatever case, what matters is that the folk who've done the thinking already don't forget to keep thinking, and that they try to persuade others to do the thinking, rather than just battering them into submission. You don't find (m)any thoughtful sexists or racists, as it goes. 

Have some of this from book IV:
“Who are you?” Gilbert asks. He indicates the chairs that they might sit on, then sits down himself. “Please, sit.”
    Astley and Ascham look at each other. Then first Ascham sits down, and Astley does the same. “My name,” Ascham says, “is Roger Ascham. Tutor to Elizabeth.”
    “And I am her governess. Kat Astley.”
    “I have heard of you.” Gilbert looks from one to the other and back. “Well, Roger Ascham and Kat Astley, I would like to know why I should help you, one way or the other.”
    Again, Ascham and Astley look at each other. It is Astley who speaks. “My mistress has not been at her ease since he left her. She wants only to see him again.”
    “Strelley,” Ascham says, “is your friend. He spoke well of you, to me, to Mistress Astley. To Elizabeth.”
    “Strelley,” Gilbert answers, “is a dead man. Thomas Seymour had him killed.”
    “Yes,” Ascham answers, “that is the story. But since he died, he saw Elizabeth when she was in the Tower. Not what one might expect of a dead man. She has not stopped thinking about him, dead or otherwise. His friends went to Rome to bring him back once before. Back from the dead.”
    “If,” Astley adds, “we were to send his friends to look for him once again, where should we send them?”
    Gilbert stares at one, then the other. “I need to understand, if I may…? This dead man, Strelley, you want me to tell you where he is. You, tutor to the princess, and you, her governess, want me to tell you how to find a man who, from what I can tell, will commit, or perhaps has already committed, treason, by absconding with your charge. So by asking me this question, earnestly as you have, you are yourselves accessory to that treason. Have I understood correctly?”
    Astley smiles. “Are you threatening us, Master Gilbert?”