You make good points here. I'll try and be as succinct as possible. Firstly, when it refers to Jesus driving out demons, don't think of this as driving out demons "the Exorcist" style. Sure, there might have been a bit of that; but physical diseases and parasites were also considered to be evil spirits or "demons" at the time, so consider it more him healing the sick and driving out parasites.

Christians love to blame "the devil" or Satan for all the ills of the world. This is kind of ridiculous. It says in Genesis that God looked over all he had made and said it was "good". The only way "Satan" could have perverted them is not by perverting the plants directly, but our perceptions of it. The Garden of Eden motif kind of applies here, even though it's obviously allegorical. There are so many stupid christians who will spout all sorts of bullshit. The idea of a malevolent entity out there who is orchestrating all the evils of the world and this evil entity has a bunch of minions to do his bidding is a little crude and the metaphor only goes so far. Humans have free will, they are capable of the most atrocious things ALL ON THEIR OWN. Humans don't need any influence to be violent or to inflict pain on someone. It's just their nature, what's automatically programmed in. It takes discipline and dedication to NOT be these things.

You said "As a matter of fact, members of one sect are quite fond of claiming that revelations of OTHER sects are indeed from satan". A quote I read the other day goes as such "When god starts to hate all the same things you do, it's obvious you're making him in your own image.". Christians are all too guilty of this one.