Simple. Sasuke is an obvious Tsundere. Naruto fell for the Tsundere when they showed physical affection for each other. Manga cliche. Post time-skip has all been for Naruto chasing the Tsundere after Naruto was physically rejected. Big impact on his life.
As for the other one, Kakashi's Thousand Years of Pain served a dual purpose: 1.) It prepared Naruto for the physical relationship with the Tsundere, and quite probably aided Naruto to make the emotional relationship get going, and 2.) It prepared Naruto for his confrontation with the Akatsuki leader. Even with said Akatsuki leader's name, he probably couldn't have had lasted a thousand years.
On the other hand, if you're looking for a real non-homosexual none-out-of-my-behind argument, I don't have that .
But I guess Iruka's nurturing is what allowed him to graduate from the academy and become part of Team 7... otherwise it would have been someone like Choji.
1. Does anyone if you think, that Madara or Zetsu is going to make an entrance on that island?
2. If Kisame tries to kill Killer Bee, is it going to be:
- a co-op Naruto / KB vs. Kisame
- KB vs. Kisame
- Mighty " Bruce Lee " entrance of Gai with his flying kick, big smile and thumbs up
... You're Dead 2 Me Now ...