Just use COMMON SENSE!
Imagine a popular fictional novel series came out, lets say The Harry Potter Series.
Now imagine that people everywhere started talking about said series and started forming organizations about discussing it. The organizations declare that Magic and Hogwarts really exist.
Everywhere you go there are people handing out fliers about "defence from the dark arts.” They even wake you up Saturday morning to try to convince you to join house Hufflepuff.
These organizations lobby for tax free status, and insist that schools acknowledge the existence of magic…and politicians who are part of the organizations grant it to them.
Magic is added to school textbooks.
In order for anyone to be taken seriously in politics they have to declare there allegiance to Hogwart’s.
Now when things happen, said politicians say “It's Dumbledore’s will.”
Wars are fought over the followers of House Gryffindore versus the followers of House Slytherin. People die for their faith in the books.
People regularly forsake medicine for magic. And whomever declares themselves a wizard and gets a wizard licence is granted societal respect. They ask for donations for the further promotion of magic and get them.
Billions of dollars worth.
When you tell them It is just well written fiction” people snort about you being just a muggle, and some even declare you a dark wizard posing as a muggle. You even get slightly discriminated against, and find it hard to find a mate who doesn't think the books are real.
Now…imagine this going on for decades.
Would you be angry with the followers of the Harry Potter books? Make fun of them?
Of course you would.