This is going to sound kind of impossible but....
...some people don't like Harry Potter.
I know, I know, how can you dislike Harry Potter? It's a wonderful series full of vibrant characters, a compelling story, great world-building, and important, but difficult moral lessons. It's helped millions of children around the world fall in love with reading, made billions of dollars, and in the long-run, made the world a better place.
Plus, books about kid wizards are just fun, as a general rule.
But some people don't like it, which is fine. You are allowed to not like things, even if they are wonderful things like Harry Potter.
I would like to comment on a few things that I've noticed about some of the people who hate Harry Potter, however.
First, when you start talking to them about it, and you say things like "Why don't you like it? Do you have a problem with JK Rowling's writing style? Or the themes of the books? Do you find Harry is an unlikeable protagonist?"
"Well, I've never read the books."
Okay, you just failed. See "Sean's Guide to Hating Stuff", then come back and let's have this conversation when you've gone through the steps outlined there.
Back? Now what do you think?
"It's juvenile. It's kids' stuff. I mean, here's what pisses me off: you have all of these adults reading what's basically a children's book- there are characters named "Longbottom" and "Higgldeyfidget*" and shit like that. So you have grownups obsessing over these books, paying money for them, paying money for the films, paying for merchandise. They DRESS up as the characters and go to events with other GROWNUPS who dress up as the characters. Look, I think these are fine children's books. But, they are children's books. Grow up, read some Cormac McCarthy, and move on with your life."
I want to note that this is a conglomeration of actual statements on Harry Potter I've had with actual people who are explaining why they feel such vitriol regarding the series.
I get pissed off about statements like this. I'm an adult. I am 31 years old. I have a job, and a wife, and an apartment. I pay taxes. I drink craft beer. I enjoy fine dining, and nice bowties, and jazz. These are all things that most people who consider hallmarks of adulthood.
I also like spaceships, and hobbits, and dinosaurs, and superheroes, and lengthy series about the trials and tribulations of a group of kids who go to a school for wizards. Speculative fiction like Harry Potter has a very important place in our society. Besides the fact that it's fun, that it provides a release from the day-to-day monotony that makes up many peoples' lives, that it allows people to imagine worlds and lives that are beyond not only the world outside of their front yard, but outside of the WORLD in some cases, speculative fiction (including "kids' books") allows us to explore IDEAS and lets us look back in on ourselves. I am a better thinker because I have spent time in the imaginary worlds of China Mieville, and NK Jemisin, and Alan Moore. I am a better PERSON because I have spent time with Harry Potter, and Frodo Baggins.
So how do you respond when someone tells you that you are childish for enjoying Harry Potter?
"Well, do you like sports?"
"Of course I like sports."
"Like football? Basketball? Baseball?"
"Yes, I have tickets to the Bears game this weekend. They're playing the Lions. I just got a new Walter Payton jersey that I'm wearing to the game. Oh! And this giant foam bear claw that says "Bear Down" on it."
"Let me get this straight- you are paying an obscene amount of money for a pair of tickets to watch grown men play a child's game (moving a ball from one end of a field to another). The two teams have each chosen a ferocious animal as their avatar. You are dressing up in a costume (your jersey) of your favorite player. When you get home, you are going to log on to the internet and draft players for your "fantasy football league" where you will be putting together a pretend team of kids-ball players. You will probably experience various states of elation and distress over the course of this season, because of a children's ball game. And I'm the one who needs to grow up?"
Chances are, this will not make the person change their mind about Harry Potter, but it should at least shut them up for a minute or two. And in the mean time you can apparate to another room.
*Higgldeyfidget is not a real Harry Potter character