Naruto most likely sees how the world around him works, and it affects his behaviour, especially since he craves for acceptance.
Notice the difference in his reaction when another guy says he likes him in part 1 vs part 2.
(Sorry for a bit poor quality, it was difficult to find an accurate translation, most were viz translations which didn't convey this convo very well). In part 1 he's just annoyed, because he doesn't like Kankurou as a person. He didn't even think about that "I like you" could have certain other implications. But in part 2 he's straight up creeped out by Kakashi saying the same thing, eventhough the meaning and intention is the same in both.
Naruto's reaction to Kurama mentioning his kiss with Sasuke was also way too over the top. Like really comical. Naruto was putting on a show in front of everyone. But whenever he's with Sasuke, he forgets all about this, he is fine with waxing poetry to Sasuke, or Sasuke being close to him...
My guess is since he went through puberty he also learned things about himself and thus started to become more sensitive to such things. Thus internalized homophobia.
Take this scene for example. He seems a bit uncomfortable being there. Sai was probably made to be like this (inappropriate, talking about p*nis all the time, being compared to Sasuke, challenging Naruto about his fixation on Sasuke) so Kishi could introduce more such themes into the manga. He's rather clever about this.
Another guess (it could be both combined) would be that since Jiraiya is so aggressively straight man (to the point he has to introduce himself by saying he's not into men lol) living with him for those years during the timeskip could have affected Naruto's mindset even more. But it's funny how Kishi keeps stressing over and over how Naruto finds Jiraiya's er*tic books boring. Also unlike Jiraiya who peeps on women for p*rverted reasons, Naruto does it as a prank, and in order to practice his oiroke no jutsu. Kishi is trying to show how they are different. I remember on one discussion forum one guy actually brought up he noticed Naruto's changed behaviour after he came back with Jiraiya! Like that he was even more gay and more sensitive to gay things. See, other people notice too.
Then he calls Konohamaru's boy-on-boy jutsu "nasty". Naturally, it's a shonen, Naruto can't have a comically interested reaction like Sakura to something like that, it wouldn't fly. Thus the internalized homophobia. But I also think he didn't want to see Sasuke who he's possessive over being with Sai like that lol. And Naruto really isn't one to talk considering what he came up with later.
Look how proud he looks. Little hypocrite. He's been working on those twink bods more than rasengan lol. Kishi wasn't very subtle with that comment. Also Kishi fought for this moment with his editors for YEARS because he just really needed to write this down. It was just that important to him...
Of course Naruto's repression comes up when it comes to Sasuke as well. Here he admits Sasuke is attractive, but then immediately backpedals on it. His real feelings just slipped.
Later, he was thinking about Sasuke, his mind consumed by Sasuke, but when Sakura and Sai appear his whole body language changes and he immediately claims he was thinking about a date with Sakura. He didn't want to be vulnerable nor let anyone know about his real feelings at the moment. He is hiding behind a heterosexual facade.
But sometimes Naruto doesn't even think of backpedaling on it. He is with his supposed "crush" yet unlike anyone else who would try to get closer or maybe flirt, he is just thinking about Sasuke. This is actually a moment that made many people raise their eyebrows. Including people who didn't like narusasu, or people who didn't ship anything. Specifically because it's written like a clickbait, as in Naruto says "he is happy" and Sakura going "huh?" and because she's his supposed crush who is taking care of him as I said most readers would expect next page have Naruto say something that would emphasize his crush on Sakura. But no, he goes on about Sasuke. No matter how much ss/nh insist we see gay everywhere, many other people picked up on Kishi's writing at many points during the story. But anyway, even with the internalized homophobia, Naruto's love for Sasuke is so strong he can say crazy things about Sasuke to other people and to Sasuke himself that things like "I'm starting to like you" (a completely average thing to say to another person) can't compare to, and still be unbothered by it.
Finally there is the interaction with Minato. Naruto wants to look good in front of his dad so he hesitantly agrees Sakura is his girlfriend, despite how in the previous arc we were shown that Naruto knew Sakura still likes Sasuke, and was angry at her when she tried to confess to him. So he is obviously not serious about Sakura being his girlfriend, but he is saying it to Minato hesitantly. Yet when his dad is leaving he doesn't want to lie anymore.... but he's also hesitant about admitting he hasn't found a girl like his mom wanted.
About the last part, I think it's referring to the armadillo scene? I think it was Kishi's typical humour, like how Naruto saw Haku in makeup and feminine clothing, and assumed Haku was a girl, but then was told Haku is a boy and went "oh okay, I didn't know that kind of thing existed". Here there was instead an armadillo that somehow looked like it was wearing makeup (??? idek or at least looked feminine) and since Naruto needed to write down whether the animals were boys or girls (a ridiculous cover up mission they made up to hide the war was going on from Naruto lol) but then it was flipped over with everyone else and Naruto saw its p*nis and went "even if heaven and earth switched places, a male is still a male". I guess Kishi likes this kind of thing lol... his d*ck jokes...
I know it says "the world might flip over" here but I know it's actually that proverb "even if heaven and earth switched places" that's often used in Japanese.
EDIT: this got flagggged by tumblr so I had to edit sus words.
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