The point is that works of fiction don't suddenly become factual if their main characters are spoken about in this context.
And there actually is a small religious following for Harry Potter: https://qz.com/788817/two-harvard-divinity-school-graduates-explore-religion-and-spirituality-in-new-harry-potter-podcast/amp/
But if you're concerned about comparisons with a "legit religion," I could also speak about Horus, Mithra, Thor, Dionysus, Krishna, Buddha, or any of the other god-man myths in the context that they were historical figures. This does not make these stories real either.