I ride in the dark all the time. You need a very good lighting system.
As for danger from people, I think cycling is rather safe. As has been pointed out, cyclists do not look like valuable targets because no one thinks they are carrying money. Another thing is cyclists are moving faster than is convenient to chase down. Generally, you see them and they are gone. Of course, the exception here are traffic lights but then you are usually not alone because of the vehicles stopped with you. You can not stalk them like you can a pedestrian (that is if you are a mugger or a predator). Also the gender of females is obvious from a long distance if they are walking or running. But the gender of a cyclist is not unless you get close (assuming you are not wearing a two piece bathing suit or something). Also, cyclist are out in the street. When one is walking, one is on the sidewalk. That is a more private spot and a mugger can get you and get your money in a place that is rather "private" or secluded pretty easily. Getting someone on the street is far more public and high risk. I would suggest that cycling is far more safe than walking home, jogging or waiting for a bus.