Why is Colombia dangerous?

Colombia is not dangerous. It is a general missconception fed by the media due to an internal conflict. But in general is not more dangerous than any other place in the planet.
Because it is a developing country with some degree of poverty, street gangs, armed conflict between guerilla groups, paramilitaries and the government and organised crime.

However only a small minority of Colombians are involved in these things, the majority of Colombians are hard working, family oriented, caring and friendly people. Colombians also have a great sense of hospitality to their guests and often treat visitors very well. You need to take some precautions when you are visiting Colombia and be alert to your surroundings, but as long as you don't hang around bad areas or go looking for trouble then you should be fine.