Zenitsu is canonically respectful of Nezuko anyone who says otherwise didn't read the manga
Anyone who says that Zenitsu is canonically not respectful of Nezuko frankly I have this to say to them
“Are we using made-up KNY now?”
Because if we ever read the manga, we can easily see that this is entirely false.
Some other commentary that usually follows this is that he treats her like an object or not a person, or as possessive or something along those lines.
Zenitsu has always canonically been respectful of her and her boundaries. That’s just look at the examples from the manga that prove this to be true.
Anyone who brings up the chasing scene as evidence that he does not respect her has clearly not read the manga because that scene is never in the manga. In fact, that scene in the anime is a direct contradiction of the manga because, in the manga, the only thing he does when he meets her for the first time is blush profusely at how pretty she is and then give her flowers.
Even after that, he is extremely respectful of her space.
When we see them talking while she’s in her box, he respects her. They have an average conversation where they exchange words and scratches between each other.
In reality, Zenitsu is one of the few people who actually treats Nezuko like an actual person—not like a demon or some kind of monster, but as a person—also not like a child or an infant, which this fandom seems to love to do with her.
In fact, he’s never actually treated her as a demon, which is something that almost no character other than Tanjiro has ever done in the series with Nezuko.
The scene in Flowers of Happiness explicitly confirms that he does not see her as a demon and also respects her as a person.
"I get it," Zenitsu murmured, preempting any explanation from Tanjiro with an unusually serious expression on his face. "It's about Nezuko, right?"
Tanjiro's heart jumped into his throat. When Tanjiro was at a loss for words, Zenitsu nodded to himself with a look that said he understood everything.
"You were picturing the day when Nezuko gets married, and you got all sad, didn't you?"
Tanjiro stared at Zenitsu, dumbfounded. "Huh?"
"Listen, Tanjiro. You can't be like that. For Nezuko's sake, just be happy for her when someone comes along to marry her, okay?"
Tanjiro still could not find the words. Zenitsu's comments slightly missed the mark. In his mind, demon Nezuko would get married like a normal girl and go off to be with her husband's family.
Zenitsu’s thinking isn’t too surprising since he has never been concerned that Nezuko is a demon.
Tanjiro was deeply grateful for his friend’s mindset, but that wasn’t quite what was troubling him. He had this feeling that there was something fundamentally, definitively different going on in his heart, but he didn’t know what it was. It just felt bad, like a small bone lodged in his throat.
This scene proves that he sees her as a human and is respectful of her, and the only thing he desires from her is her happiness.
Another scene from Flowers of Happiness that proves this even further:
He was completely immersed in strict training for full focus and partial focus breathing. This period of time, where he was able to go for a short walk with Nezuko after the moon revealed its face, was something that made him feel happy beyond words.
Also, he only dared to openly bring Nezuko out after getting permission from her older brother, Tanjiro, as well as from Shinobu, the owner of the house.
OMG! ASKING FOR A GIRL’S PERMISSION FROM HER GUARDIAN TO TAKE HER OUT ON A WALK IS SO DISRESPECTFUL OF HER BOUNDARIES.
LOCK THIS BOY UP FOR DARING TO ASK PERMISSION TO TAKE HER OUT. IT’S SO DISRESPECTFUL. HE DESERVES THE WORST PUNISHMENT POSSIBLE: JAIL! JAIL!
Another scene from Flowers of Happiness
At times like this, everything in the world seemed to shine. Even the crescent moon hanging in the night sky celebrated them.
There’s a field up ahead with tons of flowers, okay? You’re not tired?
Oh! There’s loads of white clover. I’ll make you a crown of flowers,' Zenitsu said, a rush of blood reddening his cheeks.
Nezuko looked up at him with the bamboo gag across her mouth, pushed her perfect chin forward, and nodded firmly. Zenitsu practically melted at this adorable gesture."
Omg, repeatedly asking for her consent and if she’s too tired to go out on a walk is so disrespectful.
And before people bring up “what about when he gets mad at Giyu, Inosuke, and Sanemi”:
Both of those scenes are examples of jealousy, not possession or disrespect of her boundaries.
If you notice, the only thing he does is get jealous and upset, but he never once tells Nezuko to stop hanging out with them or interacting with them. Nor does he go to Giyu, Inosuke, or Sanemi to tell them to stop interacting with her.
Nor does he ever hold a grudge against Nezuko or be mean to her for interacting with them.
If you need even further proof that Zenitsu is canonically respectful of Nezuko and her boundaries, look at the scene where he confesses his love to her:
“I love you, Nezuko-chan! I want you to be my bride! I will do better from now on, so please give me your answer in one year. I will protect you with my life.”
Let’s read that last part again:
“Please give me your answer in one year.”
Oh yes, telling a girl to take a whole year to think about her feelings for him and waiting for a response is so disrespectful and forceful of her.
He gives her a whole year people to figure out how she feels about him and give him an answer.
Because maybe and I don’t know he’s always been respectful of her, her boundaries, and her autonomy to make her own choices?
If he were canonically the opposite of those things, he would’ve demanded that she give him an immediate answer. He would’ve prevented her from hanging out with other guys and told the others to stay away from her, but he never does any of those things.
Yes, he has a problem with jealousy and immaturity, but that’s not disrespectful of her boundaries. Those are just emotions he can work on, and honestly, they’re pretty natural for an immature teenage boy with low self-esteem issues.
Edit: also thanks to @autisticzenitsu for help and inspiration for this post