It wasn't he needed character assassination in order to love Hinata, it was his character had to be destroyed so she wouldn't be seen as his second choice. SP did not want their waifu seen as the Silver medal. Since, no matter how you look at the story; Naruto only got together with Hinata once it was clear Sakura and Sasuke were getting together.
In the manga, it seemed Naruto backed off because Sasuke was finally realizing his feelings for Sakura and he wanted his two most important people to be happy. Despite him still being in love with Sakura. Then he married Hinata to repay the favor of Neji's sacrifice by marrying his widow.
In the movie, Naruto only went after Sakura because he understood Sasuke liked her...somehow? Sakura realized this sometime after the war ended and rejected him fully. Then The Last happened.
It still amazes me on these romance stories where the people constantly say "I am doing this to make the other person happy." It sounds selfless on the surface, but in reality it is the most selfish thing to say to someone. You don't know what really makes another person happy. The biggest happiness you can give someone is a choice.
The ironic thing is is this discussion is constantly pushed around in the story, but never done practically.
Naruto wanted Sakura to be happy, but he never told her how he felt.
Sakura wanted Naruto to be happy, but never asked him how he felt.
Sasuke constantly told Naruto and Sakura how he felt, and they literally ignored it in favor of what they wanted for him.
Hinata is the most selfish out of all of them, because she didn't care about anyone, but herself. Everything she did was for her infatuation, not for her love. If it really was about Naruto, she would have let him feel how he wanted instead of brainwashing him.
Hinata is the most selfish because she only cares about herself
Next is Sakura because she keeps pushing how she wants both boys to feel to the point that they have no say: "Sasuke you HAVE to love me because I love you. Naruto you HAVE to love Hinata because I love Sasuke and I don't want to feel guilty about not loving you."
Naruto is selfish because instead of living the life he wanted, he lived a life everyone told him to live whether they did consciously or sub-consciously
Sasuke is actually the least selfish in this context because he didn't care how anyone else lived as long as they didn't get in his way of his goal which they constantly did.
Compare this to Ochako with Deku. She loves Deku, but she has her own career to look into. She supported Deku in many ways and even changed a few things to support him...not because she wanted to be noticed and loved by him, but because she legit wanted to help him. THAT is is selfless love and even though she may get jealous and envious every now and them...that is just her being her.
It amazes me how Sasuke was literally open since day 1 with Naruto and Sakura and they both just legit ignored everything Sasuke was saying.
Team 7: "Sasuke, what do you want in life?"
Sasuke: "My family was murdered by my brother. I want to punish him and try to bring honor back to my family for the betrayal. I want to know the truth"
Naruto: "Man, Sasuke is a mystery. I don't know what he wants in life. I wish I was him and be popular"
Sasuke: "No, I want justice for my family and clans murder. I don't care about popularity, I just miss my family."
Sakura: "Sasuke is in love with me and he probably is too scared to admit"
Sasuke: "I actually don't care about you and have no feelings. I just want my family back."
Kakashi: "Sasuke probably just wants friends to be around since I lost mind and am miserable alone."
Sasuke: "That sucks, bro, but I just want to avenge my family."
Actually, thinking of it this way, I can see why people like Sasuke because he was being the most truthful one who actually had a legit goal. Sure, I don't agree with how Sasuke went about it, but I get it.