One of the persistent DC area myths is the one about how Georgetown would have had a metro except the residents didn't want the crime or the poor people (depending on the version you hear). Now first, as the lovely folks over at We Love DC have carefully documented, that is not the reason. (Short version geography. Long version, click the link.)
But, it is a common assertion that public transportation leads to crime increase. I'm not entirely sure why. I mean surely criminals could steal cars, assuming they did not have access to them already. So, some folks decided to study this and guess what they found. It doesn't. In fact property crime actually decreased in the areas near new stations, possibly as a result of the increase in foot traffic to the area.