Kids are going to be weird and use their imagination. They'll pretend to be an NFL player breaking tackles as they run through a crowded school hallway. They'll pretend to be Optimus Prime and pretend to transform into a truck. Or they'll pretend to be iron man blasting bad guys with their lazer palms.
The issue is when your friends have aged out of that behavior and you think it's still cool to Naruto run up to them all the time.
I've been into Anime since the 90s, always had friends and wasn't ostracized for it. Some people asked questions about tentacle hentai and Akira, but since was I never found any intereet in either all I could talk about was stuff I'd seen and I'd just tell em that.
I guess the closest thing to a real negative reaction was my mom walking in on the opening scene of Ranma 1/2 Movie 2, where Ranma, having been at the beach as a guy, was now running around topless as a woman. She didn't accept "that's really a guy who just got splashed with water."
I have a family member with a kid about to enter middle school who is very likely going to end up being this guy. We've been trying to de-weeb him, but it's not going great. I think when the ninjutsu sinks its kunai in at such a young age, it's a lost cause. My only hope now is to just make sure he knows how to run properly.