I read the first few pages of this topic and quickly became bored, so I may address points that have already been addressed and such. I have no authority to say the books are or aren't evil. This is just my own personal opinion.
(spoiler alert if you haven't read all 7 books and/or seen the movies)
I was born and raised Orthodox. My mom read the HP books when I started asking about them, then deemed them harmless and allowed me to read them. They were actually the books I learned how to read with. If you can present to me real evidence of bad themes in the book and say it's evil, then I will accept that. However, I find overwhelming evidence that the books actually have harmless, if not good, messages in them.
Harry's parents died, killed by Voldemort (the main villain), when he was a baby. They were trying to protect him. His mother's sacrifice for his life protected Harry from Voldemort until he became of adult age, because her love for him was so powerful.
In Harry Potter and the Order of the Phoenix, which is the fifth book, Harry feels angry and misunderstood by his peers, so he isolates himself from them. As he begins to isolate himself, Voldemort's hold over him grows stronger, and he begins to feel even more angry and misunderstood. He approaches his godfather, a man by the name of Sirius, and asks Sirius if his anger makes him an evil person. Sirius says "Harry, the world isn't split into good people and Death Eaters. We all have light and dark inside of us, what matters is the part you choose to act on." (The Death Eaters are Voldemort's followers.)
Also in HP and the Order of the Phoenix, there's a scene where Voldemort tries to 'possess' Harry. He makes Harry think of all the awful and horrible things in his life, all of the deaths and the misery. Harry is about to give in and let Voldemort win the battle when his friends enter the room. Upon seeing them, Harry remembers his parents, all of the great times he's had with his friends, his father figures in his life and his love for all of those people. He tells Voldemort, "You're the weak one. You'll never know love, or friendship, and I feel sorry for you." The love is painful for Voldemort to come into contact with, so he recoils and leaves Harry's body.
JK Rowling also mentions many times over an afterlife. Harry was approaching his death, about to sacrifice himself for his peers so that no one else would have to die, and he saw the ghosts of his parents, his godfather, and another strong father figure in his life. They told him they had been watching him all along and not to be afraid of dying.
Voldemort, to protect himself, has split his soul into seven pieces (by killing people) and placed them into objects that are nearly invincible. As long as those objects exist, Voldemort cannot die. Harry and his best friends, Ron and Hermione, set out to destroy the objects so that they can defeat Voldemort. The objects don't go down without a fight: they play on the weaknesses of the person trying to destroy them, making them see visions or trying to make them doubt themselves, trying to make them turn on their friends, trying to plant seeds of doubt. Each of the times that they come across a piece, Voldemort's soul tries something different to stop them, and by various different means the trio of heroes overcomes the temptations. JKR stresses the importance of keeping the soul whole and intact, and that evil is necessary to break your soul apart.
There are also creatures in the series called "dementors". Dementors live by sucking out the souls of people, which they do by feeding off of the bad things in their life until that's all the person can think about. The way to defend yourself against a dementor is basically to think about your happiest memory. The more powerful your memory is, the more powerful your defense will be. The memory Harry chooses is a very vague memory of his parents speaking to him when he was an infant--because of the love his parents had for him and how happy having a memory of his parents made him, his defense against the dementors was the strongest of any other character in the book.
There are many more examples I could give, but these are the first to come to mind.
Love and friendship conquer all. This is the constant theme of the books and it proves itself time and time again in many situations against many foes with many motivations.
On the other hand, the 'witchcraft' in the book is fantasy magic. Turning the tip of a wand into a flashlight, making objects hover, making pictures move. I have known two Wiccans in my lifetime, and the magic they practice is extremely different.
As a young child, I read the books and mainly dismissed the magic. "Oh, a light on the tip of a wand, that's sort of neat, I guess." And on the flip side--"Wow. 'We all have good and bad inside us, what matters is what we act on'--that's a really, really good quote!"
Also, I am very curious about the statistics mentioned and how the person who did the study decided upon them. What questions were asked? "Are you a Wiccan?" and "Have you read Harry Potter?" That's an unfair study to make, because they could have read Harry Potter after they became interested in witchcraft. Besides, more people have read the books than not, so there could be absolutely no correlation between the HP books and the witchcraft.
Youtube is also an incredibly unreliable source for this kind of thing, because you have basically have no clue who's posting it or what their beliefs are. When it comes to religious questions, I would much rather refer to an Orthodox website than leave myself vulnerable to the opinions of someone who could have a huge agenda I don't know about.
Now, if you have actual examples of evil events or quotes in the book (other than that which is obviously evil and comes to be triumphed against, such as Voldemort), feel free to use those as evidence.