You think that God should somehow prevent evil. He should actually stop the murderer and the rapist. This is because you (understandably) consider those two acts to be evil. How about the liar and the thief, the fornicator, pornographer, blasphemer, and the adulterer? Do you think that they are evil and should be stopped? God considers them to be extremely evil. But that's where conversion comes in (the new birth spoken of in John 3). God miraculously removes the hatred from the heart. He changes us on the inside so that we want to stop doing all evil. So how sincere are you in your desire to see evil stopped? Are you prepared to start with yourself?