"Agreed, the second is almost the opposite of the first. If you had instead said "There is a difference between "allowing" them to do evil, and not preventing them from following their own, malign, intentions", I would disagree because not preventing somebody from doing something when you could have is the same as allowing them to do it. If I see somebody planting a bomb on a plane and I don't inform the authorities, am I allowing them to do evil or am I not preventing them from following their own malign intentions. I would suggest there is no difference between those two and the fact that you claim there is exemplifies the mealy mouthed excuses that you Christians try to put up to defend the actions (and inaction) of your alleged god."
God does not interfere with our actions, because, good or evil, we make our own decisions. That applies to whether you decide to prevent someone from doing a certain action, or not, and why. If God stands over us and controls everything we do, then life is hardly worth living, making us little more than robots. What we do with our freedom to act is up to each individual, and how he sees life and morality, right and wrong.