i do believe in God. and yet there is also extreme evil in the world.
if you believe in the God described in the Bible, it's pretty inconsistent not to believe in opposing forces of good and evil. and of course the Bible speaks about both angels and demons. i think that there are both people who underestimate and others who overestimate the activity of either or both angels and demons. i don't attribute all bad stuff in the world to demon activity, but i do think that in some cases that is not only possible but probable.
some bad stuff just comes from the fact that all of us have a human nature that is capable of doing right or wrong. and far too often, humans choose wrong - what the Bible calls sin. hard for any of us survivors to deny that one - whatever you want to call it. and ultimately - all evil, sin and bad stuff can be traced back to going against God - whether it is Satan, demons, sin or human nature.
that's how i see it.
"Tell your heart that the fear of suffering is worse than the suffering itself... And that no heart has ever suffered when it goes in search of its dreams, because every second of the search is a second's encounter with God and with eternity." - Paulo Coelho