What is the name for this fallacy?

It’s something I have commonly found myself making.

1.) Johnny gets a new Chemistry teacher. Over the few weeks he finds out she’s has an okay personality but is a bit harsh when needed. He learns through her discussions with the class that she’s very ‘intelligent’ and educated. She never got less than a B in Middle School. She graduated top of her class in school, got a good course which had many high financial prospects but she settled to be a teacher. She’s also a young attractive teacher.

Over the few months, she gets quite frustrated with the class and angry. She uses gendered slurs and idiomatic expressions like ‘Man up’ ‘Toughen Up’, ‘Grow Up’. A long with that, she has an exploding temper at times and gives detentions when really angry.

He’s surprised. Aghast. Not because she’s getting angry and that she isn’t the perfect nice teacher he once thought she was, but simply he finds it inconceivable that someone with who had attained such a high level of academic qualifications along with looks, would still hold ‘old school’ beliefs. He has always had it in his mind that a young millennial woman, non religious who is considered good looking, has a high self-esteem and seems intelligent would have a very agressive personality that usually correlates to him with older individuals who are religious, come from a less financially well off area and are less educated.

Is it generalizations or something else?

And she has brown eyes?

Why does everything have to be a “fallacy”? He was stereotyping beautiful smart millenials. Ok so the “stereotype fallacy” is now ready for the internet logical fallacy lists.

Kind of like judging a book by it’s cover. It’s not really a fallacy.

Not quite a debate, but not quite GQ. Moved from GD to IMHO.

[/moderating]

The only fallacy I can see here is the notion that this line of reasoning is fallacious. It’s seems quite reasonable to be surprised if somebody turns out to have beliefs or personality traits that are incongruous.

There might be an element of stereotyping, but I don’t really think this example qualifies. For example:

“I can’t believe you’re Irish and you don’t like getting drunk on Guinness?” - stereotyping.

“I can’t believe you’re gay but you voted for Mike Pence” - not stereotyping, just rationally questioning how this person reconciles two seemingly incongruous elements.

But even stereotyping is not really a fallacy, depending on the stereotype it lies somewhere along the spectrum of poor reasoning and offensive prejudice.

Johnny is going to be disappointed quite often in life.

There’s no logical fallacy. Johnny was reasoning from a false premise.

…but to be fair, she looked god in a false premise…
…-d&r-

It’s called millennial snowflakialus.

My teachers didn’t really confide in us that much.

Wait, she was sharing her MIddle School grades with a bunch of students? And the fact that she’s young and attractive? And her financial goals? And her religious beliefs?

Or… was this learned through extensive research online?
(little Johnny says extensive, his therapist might say obsessive…)

How many of these details were provided by the teacher or assumed by ‘Johnny’ because he liked the teacher initially? And if the teacher provided such details maybe ‘Johnny’ didn’t realize she was also a liar.

Actually, this is sort of true. My teacher did share her grades with us.

Probably bullshitted most of it but…

Wait! What? It was you? You’re Johnny? I never would have guessed.

You think that a fallacy is just some nerd’s list, like a TV Tropes page? Fallacy has an actual meaning in logic.