In reality, no one is stopping you from reading Potter. If you are fretting because some people say you aren't a Christian because you read Potter, the problem is with YOU, not them. They have the right to their opinion, right or wrong. Claming you have been harmed is rather hyperbolic. I read Potter and I'm not offended if someone says I'm not a Christian. They are entitled to be wrong.
What is offensive is using slurs like "fundie" and "fruitcake" to describe people who don't like Potter. Also, claiming that people who don't like Potter are involved in a vast conspiracy to deny First Amendment rights to people is equally offensive.
No one is stopping anyone from reading Potter. And it's ridiculous to blame people for something that isn't happening.
There are a lot of people out there, of all ages, who like their entertainment to be escapist, because they don't particularly like this planet. Then they come back to reality and live well-adjusted lives. That kind of person wouldn't want the magic to be real. It's hard to explain to an outsider, but we don't want the spells, just the spaceships. Fantasy looks inward; science fiction looks outward. There are hundreds of people who were inspired to careers in science and math because they read Heinlein as children; I have never met anyone who became a sword-wielding mage because he read Tolkien.