Dumbledore did, with great severity and understanding of consequences, what most of us in his position would have been unable or unwilling to do. He "raised him (Harry) in the way he should go", preventing Harrys murder while giving him every chance and training to win.
Good and powerful men who do nothing may as well just let Voldemort win.
Dumbledore did what had to be done, at great cost to himself, to those he loved, with the full weight of that knowledge over him always.
I don't care for the Potter books at all, and I've read all of them (Hermione should have been the protagonist. An interesting spin would be that she manipulated Potter the whole time).
Someone thinking Dumbledore is evil is someone who doesn't understand that good sometimes comes at a great cost, that with love can come great sacrifice, and we pay it gladly to prevent the wicked from grinding us under their heel.
I'm sure in the land of Gummi bears and sugar, evil is vanquished without losing one second of sleep.
In the Potterverse, it's not so easy.
In the real world it is even less easy.
The books still suck though.