I'm not going to go into my thoughts on this because I, too, don't want to get angry.
I'll instead take what my (once) homeschooled, 20 year old, christian, harry potter LOVING friend has said on the subject in the past.
The Harry Potter world is an alternate universe from ours. It's a world where magic exits and is, in a way excepted in culture and society. It has a history of wizards to the point where it is completely and utterly NORMAL for them to exist.
As long as one takes that into account when reading then I think nothing's harmful about them at all.
My friend wasn't allowed to read the books until she was 15, once she started she, as said, didn't see anything harmful. Wasn't shocked by them, nor did she feel pulled to believe them as law.
My cousin, my age, conservative and homeschooled was under similar ban until this past month. He's wolfed down the first 5 books in that span of time and seems to enjoy them a lot.