This. It wasn’t the goofiness, it was the content. Something about politics, maybe, or something about laughing at a particular category of people (or at *any *people in general). Or a word you used in describing someone.
T-Minus - Am I remembering correctly that you’re autistic?
Was she doing something she wanted to focus on- reading, work, a hobby?
You kept interrupting her and didn’t pick up that it was annoying, so she had to be blunt about it? Maybe this is a recurring pattern?
Just guesses.
…or she doesn’t like his taste in porn…
There’s something she doesn’t like about you. And now you know there is something you don’t like about her.
Straight-up, unvarnished honesty isn’t always a virtue. Her statement was textbook passive-aggressive and just plain mean. And immature. Grownups know about tact, kindness, and effective communication. How old are y’all?
She could have gotten the same message across with something like, “I love your sense of fun and how you can be silly sometimes, but it’s when you’re serious that I’m the most attracted to you (or find you the sexiest) (or want to kiss you all over) (or whatever kids say…).”
The Mean Girl in me wants you to have replied, “When you say cruel, passive-aggressive things like that to me, it makes me regret being in a relationship with you.” But that wouldn’t be the right thing.
Of course we don’t know how many times she’s tried the more gentle approach.
Sometimes you get to the place where you just have to say “I don’t like this”. The relationship part was not the greatest, I admit, but I wouldn’t be surprised if there isn’t more backstory here than the OP lets on
She is using the word goofy to mean something else. That something is probably behavior on your part that you’ve done for a long time without really being conscious of it.
None of this means that your relationship cannot be mended. You need to have a heart to heart with her about just what it is that she means when she uses the word “goofy”…actually, you don’t need to even make it about that word, you can just ask her what behavior of yours makes her uncomfortable. And try to dial it back.
The effectiveness of this strategy will depend on how old/emotionally-mature you both are.
Yeah, I’d think the OP hasn’t noticed other signs of a problem. Or maybe this relationship just started and this is her way of saying it’s not going to go any further. Otherwise I’d think the OP would now realize it’s not the first time she wasn’t all that thrilled with him and just the first time that he noticed, like a ‘break the glass’ moment where the fog of infatuation lifts and people see each other clearly for the first time.
Maybe she was just in a pissy mood and taking her aggression out on you, or maybe she was annoyed she wasn’t in on the enjoyment you were getting from the video. It could be a lot of things, you should have a conversation with her.
Not sure if I’m being Poe’s Law’d here, but this is utterly clear and straight - she doesn’t like your goofiness, and you should no more be insulted by her telling you so than you should feel insulted by a doctor for telling you that you have liver disease. She is telling you something you need to change, and warning of consequences if you don’t.
To further elaborate: It may be passive-aggressive for her to state it like that, but it is even more passive-aggressive to feel irritated or victimized when someone expresses their true feelings or thoughts, as if being offended somehow negates the truth of the feeling.
Not attacking the OP, just saying.
Nope. She is telling him something that she does not like. That much is fine.
It could just as easily be “when you read poetry you kinda make me regret going into a relationship with you…”, or “when you cheer watching hockey games you kinda make me regret going into a relationship with you…” or “when you watch Doctor Who you kinda make me regret going into a relationship with you…”
He can consider changing for her. Or he can conclude that what is being called “acting goofy” is a part of who he is that he does not want to change, for her or for anyone, that his “goofiness” is part of the package. They should have a serious open conversation about it. It may simply be that they are not a great fit. Better to know that earlier than later.
But one does not need to change their personality, their interests, or their sense of humor, because a romantic partner says they do not like that aspect of you.
Oh, I think we are past phase 1 and 2. We are well into 3. Her head is telling her you are a lost cause. Her heart is still trying to fix you. Expect shopping trips to change your wardrobe and visit to her family’s home, on the way there you will undergo a lecture of mammoth size, on how to act, what to say and how to eat. On the way home you will endure another talk about how stupid you were. Good luck with that.
Q: Why did Mickey Mouse break up with Minnie Mouse?
A: She was Fucking Goofy!
I knew that one was coming!
There’s nothing insulting in what she said. She told you how your behavior makes her feel, now whether you intend to change this behavior or not is up to you.
IMO, it’s a very good thing that she would communicate her feelings in a straightforward way. I know that being very direct with your partner isn’t everybody’s cup of tea (especially in the USA) but it’s still much better than the alternative.
Did the arched back and teeth-clinched grimace give it away? 
Unless you have a really obnoxious laugh, there’s something else going on here.
I hang out at r/relationships a lot. Occasionally, someone will post a complaint about a significant other’s sense of humor. Maybe it’s overly sarcastic or juvenile or corny. Or maybe they try to be funny when “funny” isn’t appropriate. Everything else about that person can be great. But it almost doesn’t matter because they are driving their girlfriend/boyfriend absolutely nuts.
Thing is, usually the complainer has given them a number of clues, but they don’t register. And then finally they have to be brutally honest when they are pushed to the edge.
I have a friend who laughs really hard and long at things that don’t seem all that funny to me. She’ll start cracking up at something she’s thinking about and I’ll be almost afraid to ask her what’s funny because I’m worried I won’t be able to fake laugh convincingly. Now, this is no biggie in the grand scheme of things. I know my friend is just being herself. And I’m a big goof myself. But sometimes all the goofiness annoys me. I would never tell her so. But I think if I was in a serious relationship with her and we lived together, I probably would.
I don’t find the phrase “act goofy” (as used by either the OP or his gf) to be straightforward or direct. It certainly doesn’t give me information to understand why she took offense, or what he should be more careful about next time.