This is a great question and I would love if other people weighed in with their advice because I am not always certain on how to approach this either, mostly because it can be REALLY difficult when someone throws their lack of intelligence right in your face, in person. It’s just like you said—the speechlessness! You spend so long thinking, “Really? Did you just say that?” that sometimes the moment has passed by the time you’re ready for a response.
I think people who say this kind of bullshit (because that is exactly what it is) aren’t looking to be swayed from their opinion. At least, they rarely are. They just want to hear their own. Because people who are interested in thoughtful discourse and opening their minds don’t BEGIN their thoughts with statements like, JUST FOR A RANDOM EXAMPLE, “where are the real stories, you know the ones about boys and by them” or utter the words “vapid girls” when talking about YA.
Which then puts you in the position of—is there a point in saying anything at all?
I think it’s always okay to point out when someone is being a jerk or hateful or rude or when they’re wrong, especially if how they are wrong is damaging and hurtful. If they are being aggressive about it though, and you think the discussion would devolve into something really unpleasant or unsafe, you do not have to engage.
Your approach (or non-approach) is going to depend a lot on theirs.
1) asking them to repeat themselves. “What did you say?” Make them say the stupid thing twice! Maybe they will actually hear how dumb it sounds the second time? (This is more often than not wishful thinking but sometimes it works!)
2) You can ask them why they feel that way, but prepare for the possibility of getting an even more ridiculous response in return. As in, “Because YA is about vapid girls, OF COURSE!” with no further elaboration.
2 a) In which case you can just say, “Oh,” and physically remove yourself from the conversation, which is basically a declaration that their opinion is not even worth the time to pursue. I think if you are dealing with someone who doesn’t want to hear other viewpoints/is interested in discussion—and you’ll know that when you see it—then there is no point in continuing the discussion. Put your energy where you CAN reach people and make a difference.
3) If you feel there is still hope—and this is a possibility too—ask them if they have read YA. This is where they will usually give themselves away. They either haven’t or they think YA is The Cat in the Hat. This is where you get to tell them they haven’t read YA and they don’t know what they’re talking about! State it like it’s a simple fact because it is. Not meanly… it’s just a fact.
How they respond to that will, again, determine your response.
if they are genuinely interested in understanding why their logic is flawed, you might want to share some YA books they could read, classics that would be categorized as YA today, and why YA deserves more credit. This would be the best outcome!
If they come back insistent on their dumbness—that YA can’t be deep, that girls stories are vapid etc etc—just repeat yourself: “You don’t know what YA is. When you know what you’re talking about, I’m happy to have this conversation!” Maybe this person will think about it and try to educate themselves. Because THERE ARE TONS OF RESOURCES OUT THERE for them to not be so misinformed about this. They have less excuse to be stupid than you have an obligation to educate them. Maybe they won’t educate themselves. The thing is, you’ve given them enough that they COULD expand their own line of thinking—if they want to.
Which does not make the whole experience any less frustrating, I know.