I'm not particularly disturbed by IT, I adore the story, I think that it addresses a lot of things that mean something and really does strike a chord inside many people.
This is an important novel for that particular generation who grew up when Steve did, the fact that it is so relevant to me who came along much later shows how powerful the essence is, at least in my opinion. Maybe people find it disturbing because there's so much reality behind it.
There is a lot of stuff that is evocative as well as provocative, the message that evil is always in plain sight for all to see is what the story reminded me. Sometimes it just needs the slightest push or the simplest excuse to reveal that often unstable nature of the human being.